CommCell Performance Tuning

Table of Contents

Overview

You can improve the performance of data movement operations using the parameters described below. You can use one or more parameters at a time.

Basic Tuning Suggestions to Maximize the Backup Performance

The following section provides several parameters to improve your backup system performance and avoid bottlenecks.

On a Subclient

Use Multiple Data Readers

  • Data Readers

    Data Readers determines the number of parallel read operations while the data is backed up. Configuring multiple data readers per subclient on disk arrays can improve the backup performance of clients.

    Modify the number of data readers on a subclient to twice the number of tape drives.

    See Streams - Getting Started for instructions about how to modify the value.

  • Allow multiple data readers within a drive or mount point

    Configure multiple data readers for a disk array that contains several physical drives that are logically addressed as a single drive. This allows you to take advantage of the fast read access from the array.

    See Streams - Getting Started for instructions about how to enable this option.

Network Bandwidth

  • Network Agents establish data pipes to transfer data from the client to the MediaAgent. Therefore, increasing the number of Network Agents increases the data transfer throughput from the client.

    Depending upon your environment, change the Network Agents value to 2 or 4.

    See Network Agents for instructions about modifying the value for network agents.

On a Storage Policy

  • Device Streams

    Device Streams are logical channels that connect client data to the media where data that is secured by backup operations are stored.

    On Storage Policy, set the device stream to twice to the number of tape drives or writer of all libraries those are defined in the storage policy copy.

    See Setting the Device Streams on a Storage Policy for instructions about how to modify the value.

  • Stream Randomization

    Use Stream Randomization to choose device streams randomly for backup operations. This increases the rate of data transfer by backing up data to more number of parallel streams.

    See Configuring Stream Randomization.

  • Incremental Storage Policy

    Enable Incremental Storage Policy on Storage Policy properties. Once this option is enabled, the selected storage policy is used to perform incremental and differential backups.

    See Enabling Incremental Storage Policy.

On a Storage Policy Copy

  • Multiplexing

    Enabling multiplexing allows multiple backups to run in parallel to a single tape drive. This results in better usage of the tape drives, especially when the backups are from slower clients. This helps in better overall throughput and reduction in the backup window.

    For LAN backups, make sure that the network between the clients and MediaAgent is capable of supporting multiple simultaneous backups.

    • Typical multiplexing factors are set between 2 and 5 on 100BaseT networks.
    • Typical multiplexing factors are set between 5 and 8 on 1000BaseT networks.

    See Configuring Data Multiplexing.

  • Multiplexing Factor

    You can determine the multiplexing factor by analyzing the network configuration and the required disk throughput. For better performance of backups, set the multiplexing factor to twice the number of tape drives.

    See Configuring Data Multiplexing for instructions.

  • Use Device Streams rather than multiplexing

    Enable Use Device Streams rather than multiplexing to copy the data streams on each available drives first and then on used drives.

    See Configuring Data Multiplexing.

On a CommCell

On a MediaAgent

Increasing streams for concurrent backups

Improving Throughput to Storage Media

The throughput to a storage media depends on the speed at which chunks are written to that media and the number of entries per chunk in the Index Cache.

Increasing Chunk Size

A chunk is the unit of data that the MediaAgent software uses to store data on media. For Sequential access media, chunk is defined as data between two file markers. By default, the chunk size is configured to get the optimal throughput to the storage media.

The following table gives default chunk size for tape and disk backups and the recommended range of chunk size:

Storage Media Backup Type Default Chunk Size Recommended Range of Chunk Size
Tape Granular Backup 4 GB 8 GB, 16 GB, 32 GB
Database Backup 16 GB 8 GB, 16 GB, 32 GB
Disk All Backups 2 GB ----
Direct Attached NDMP All backups 4 GB ----

Even though a higher chunk size increases the throughput. granular restores (for example, single file restore) become slower. However, large restores, like a full-machine rebuild, become a bit faster.

 We recommend a lower value for frequent checks of slower backups, especially when data is moving across a WAN link.

Setting the Chunk Size for the CommCell

Use the following steps to modify the chunk size for the CommCell:

  1. On the ribbon in the CommCell Console, click the Storage tab, and then click Media Management.
  2. In the Media Management Configuration dialog box, click the Chunk Size tab, in the Agent Type column, select the <Agent>, and then enter the appropriate chunk size value.

    This value applies only to tape media.

  3. Click OK.

Controlling the Chunk Size in the MediaAgent

Use the DMMBCHUNKSIZE additional setting to control the chunk size of the data write operations that go to the MediaAgent on which the additional setting is created.

The chunk size that is specified in the additional setting overrides the values that is specified in the chunk size set for the CommCell in the Media Management configuration.

  1. From the CommCell Browser, expand Storage Resources | MediaAgents.
  2. Right-click the appropriate MediaAgent, and then click Properties.
  3. In the MediaAgent Properties dialog box, click the Additional Settings tab, and then click Add button.
  4. In the Add Additional Settings on Windows Client dialog box, in the Name box, type DMMBCHUNKSIZE.

    The Category and Type details are automatically populated.

  5. In the Value box, specify chunk size value in MB (for example, 1024 MB and 2048 MB).
  6. Click OK and click OK to close the MediaAgent Properties dialog box.

Controlling the Chunk Size on File Server

The values established for the NAS NDMP iDataAgents in the Media Management Configuration dialog box applies to the library that is attached to the MediaAgent.

Do not reduce the default chunk size for data movement

For other file servers, the chunk size is based on the size of the tape that is used to back up the data. This is not configurable.

Use the following procedure to modify the chunk size for filers that support restartability:

  1. From the CommCell Browser, expand Storage Resources | MediaAgents.
  2. Right-click the appropriate MediaAgent, and then click Properties.
  3. In the MediaAgent Properties dialog box, click the Additional Settings tab, and then click Add button.
  4. In the Add Additional Settings on Windows Client dialog box, in the Name box, type nCHUNKSIZE.
  5. In the Value box, specify chunk size value in GB (for example, 4 GB).
  6. Click OK and click OK to close the MediaAgent Properties dialog box.

Controlling the Chunk Size for Data Path

The chunk size that is established at the data path level overrides the chunk sizes that are established for the various Agents.

Use the following steps to modify the chunk size for data path.

  1. From the CommCell Browser, expand Policies | Storage Policies.
  2. Right-click the appropriate storage policy copy, and then click Properties.
  3. In the Copy Properties dialog box, click the Data Paths tab.
  4. Select a data path, and then click Properties.
  5. In the Data Path Properties dialog box, under Chunk Size section, select Use specified value, and then enter the value in MB.
  6. Click OK and click OK to close the Copy Properties dialog box.

Increasing Block Size

MediaAgents can write to media using different block sizes if the operating system that is associated with the MediaAgent on which the library is configured supports a higher block size. Increasing the block size increases the speed of write operations to tape media. The default block size for write operation is 64 KB. For mount paths, block size is the buffer size used for each write operation. (The File system allocation unit size is decided when the volume is formatted.)

Before increasing the block size, ensure that the following criteria are satisfied:

  • New block size is supported by the Host Bus Adapter Driver installed in the MediaAgent and the tape device. The most commonly used values are 128 KB or 256 KB.
  • All the MediaAgents that are associated with a Storage Policy support the block size that is configured on that storage policy
  • If different MediaAgents are used for backup and restore operations, and the backup MediaAgent has higher block size, then ensure that the restore MediaAgent is configured with Host Bus Adapters, and that tape drives that are able to read the data written with higher block size.
  • If you want to modify the block size, use the following supported values of block size:
MediaAgent Supported Block Size
ONTAP 6.5 NetApp Appliances* 64 KB or lower
DART 5.3 EMC filers* 128 KB or lower

* If you specify a block size that is larger than the allowed limit, the NAS backup process automatically changes your entry to the maximum allowable block size.

Increasing the Job Manager Update Interval

The Job Controller window displays all of the current jobs in the CommCell. A status bar at the bottom of the job controller shows:
  • The total number of jobs
  • The number of jobs that are running, pending, waiting, queued, and suspended
  • The high and low watermarks

This information is updated at the close of each chunk, or within 5-minute intervals, whichever occurs sooner.

When larger chunks are configured for data movement operations, the amount of time between Job Manager Updates is automatically extended by that configuration.

Modify this interval to increase the performance of data movement operations.
  1. On the ribbon in the CommCell Console, click the Configuration tab, and then click Job Management.
  2. In the Job Management dialog box, click Job Updates tab.

    For Agents:

    1. In the Protection (Mins) column, increase the integer value to modify the update interval for data protection jobs.
    2. In Recovery (Mins) column, increase the integer value to modify the update interval for data recovery jobs.
  3. In the State update interval for ContinuousDataReplicator box, click the integer value in the box to change the time.
  4. Click OK.

Optimizing Collect File Creation

The Collect File records the path and name of each scanned file that is included in the backup. When you back up large amounts of data, large collect files are generated. You can divide the content into several smaller collect files to reduce the time taken by a data reader to read the collect file.

By default, the number of collect files is equal to twice the number of data readers (2 x Number of Data Readers). Two is a multiplication factor which is the number of Collect files that are created for the job. You can change the multiplication factor.

  1. From the CommCell Browser, expand Client Computers.
  2. Right-click the appropriate client, and then click Properties.
  3. In the Client Computer Properties dialog box, click Advanced.
  4. In the Advanced Client Computer Properties dialog box, click the Additional Settings tab, and then click Add.
  5. In the Add Additional Settings on Windows Client dialog box, do the following:
    1. In the Name box, type For_Multiple_Reads_On_Disk_Collect_Split_Multiplication_Factor.

      The Category and Type details are populated automatically.

    2. In the Value box, specify the value for the number of Collect files that need to be created for a job.

      The default value is 2.

    3. Click OK.
  6. Click OK and then click OK to close Client Computer Properties dialog box.

Configuring the Application Read Size

Application read size is the size of the application data read from the clients for data transfer during backup operations. Values for Application Read Size must be in the power of 2; minimum value is 64 KB, maximum value is 4096 KB (4 MB).

Note that each application internally allocates a buffer size that is suitable for handling the application data. When the size of the application data read during backup operations matches the source application's internal buffer allocation then the overhead is minimized. So to achieve optimal rate of data transfer during backups, configure this value based on the source application's buffer allocation.

The value of application read size may be increased to reduce the amount of data read from the given application, which in turn reduces the amount of I/O operations performed against it. As a result, overall backup performance may increase. However, backup memory usage may also increase, which may inadvertently consume additional resources from the application. Thus, it is recommended that this value be set at either the default value or match the block size directed by the application.

This configuration is supported for the following agents:

  • Microsoft Windows File System iDataAgent
  • Microsoft SQL Server iDataAgent

Modifying the Application Read Size

The Application Read Size entered here should match the Maximum Transfer Size. For more information, see Enhancing Performance during Backups.

Use these steps to set the Application Read Size:

  1. In the CommCell Browser, expand Client Computers > client > File System. Click defaultBackupSet.
  2. Right-click a subclient, then click Properties.
  3. Click the Storage Device tab, then Data Transfer Option.
  4. Select Application Read Size, then select its value.
  5. Click OK.

Unbuffered IO for Disk Libraries

To increase the speed of operations that access the mount path, you can configure the MediaAgent to bypass the Microsoft Windows file system buffering.

This is applicable for Windows MediaAgents and disks that are mounted directly (not UNC paths).

To enable unbuffered I/O on a mount path:

  1. From the CommCell Browser, expand to Storage Resources | Libraries | <Library>.
  2. Right-click the appropriate mount path, and then click Properties.
  3. In the Mount Path Properties dialog box, on the General tab, click Use unbuffered I/O, and then click OK.

To control the number of read ahead buffers in the unbuffered I/O mode:

The read streams for deduplication jobs are not unbuffered. Therefore, this additional setting does not have an effect on deduplicated data and in completion of Auxiliary copy jobs of deduplication data sets.

  1. From the CommCell Browser, expand to Storage Resources | MediaAgents.
  2. Right-click the appropriate MediaAgent, and then click Properties.
  3. In the MediaAgent Properties dialog box, click the Additional Settings tab, and then click Add.
  4. In the Add Additional Settings on Windows Client dialog box, select the following:
    1. In the Name box, type dwMaxAsyncIoRequests.

      The Category and Type details fill automatically.

    2. In the Value box, specify the value for number of read ahead buffers.
  5. Click OK and click OK to close the MediaAgent Properties dialog box.

Increasing Data Transfer Throughput from the Client

You can increase the data transfer from the client to MediaAgent.

Increasing Network Agents

The Network Agents establish data pipes to transfer data from the client to the MediaAgent. Therefore, increasing the number of Network Agents will increase the data transfer throughput from the client.

If required, modify the other network parameters of the client, such as network card speed, network switch speed etc., to get the optimum data transfer throughput.

All subclients except those using NAS iDataAgents support network bandwidth throttling.

To set a limit for network bandwidth and the number of concurrent network agents for a subclient backup operation, perform these steps:

  1. In the CommCell Browser, expand Client Computers > client_name > agent.
  2. Click a backup_set_name, then on the backup_set tab, right-click a subclient and click Properties.
    • If your iDataAgent is DB2, DB2 MultiNode, Informix, Oracle, Oracle RAC, SAP, or Sybase, right-click an instance, then click Properties.
  3. Click the Storage Device tab, then the Data Transfer Option tab.
    • Set the maximum number of Network Agents to run concurrently when performing a subclient or instance backup.
    • Select the Throttle Network Bandwidth (MB/HR) option, then enter the throughput limit as needed. Note that the SnapProtect software throttles the transfer on a per-network-agent basis.
  4. Click OK to save your changes.

Increasing Network Agents on a MediaAgent

If you increase the number of network agents on a MediaAgent, more CPU cycles and RAM are consumed. This will result into less number of backups getting completed on the MediaAgent. If you are expecting additional backup operation on a MediaAgent, it is recommended to set Network Agents to 1.

Increasing the Pipeline Buffers

The data pipe buffers setting configures the amount of shared memory allocated on a computer for data pipes. The size of each buffer is 64K. By default, 30 data pipe buffers are established on each server. You can increase the data transfer throughput from the client by increasing the number of data pipe buffers.

When you increase the number of data pipe buffers, more shared memory is consumed by the client or MediaAgent. This may degrade the server performance. Therefore, before increasing the number of data pipe buffers, ensure that adequate shared memory is available. You can optimize the number of data pipe buffers by monitoring the number of concurrent backups completed on the server.

Use these steps to set the number of data pipe buffers:

  1. In the CommCell Browser, expand Client Computers.
  2. Right-click the client, then click Properties.
  3. Click Advanced.
  4. On the Additional Settings tab, click Add.
  5. In Name, enter nNumPipelineBuffers. Press TAB.
  6. In Value, enter a number between 30 to 1024.
  7. Click OK to save the setting.
  8. Click OK to close the dialog box.

Configuring Windows Servers for Better Performance

Configuring for Best Performance of Background Services

When the MediaAgent and CommServe are installed on Windows Server 2003 or 2008, follow the steps given below to improve the performance of background services:

  1. Open the System Properties dialog box.
  2. Click Advanced tab.
  3. Under Performance, click Settings.
  4. In the Performance Options dialog box, click the Advanced tab.
  5. Select Background Services.
  6. Click OK.

Optimizing Data Movement Performance

The following sections provide guidelines to improve the performance of backup and restore operations.

File System iDataAgent

Follow the steps given below to improve the data movement for a File System iDataAgent:

  1. It is recommended to verify the disk performance using the DiskReadWrite utility available in resource pack. For more information, refer to Resource Pack.
  2. If the client computer has multiple disks, create multiple subclients. This will enable the parallel data movement operations from the client.
  3. Configure multiple data streams for the storage policy that is assigned to the subclients. For more information, refer to Change the Maximum Number of Data Streams.

    If the Storage Policy is not configured for multiple data streams, then subclients will perform the data protection operations one after the other in a serial.

  4. For Windows and Unix File System iDataAgent, configure the subclient for multi-stream backups. By default, multi-streaming is not configured for clients with a single disk. However, you can choose to override the default configuration. For more information, refer to Streams.

HP-UX File System

For the HP-UX 11i v3 file system, do the following steps to improve the performance of backup operations.

  1. Install the PHKL_41700 patch.

    The select(2) system call enhancement is delivered through the PHKL_41700 patch.

  2. Enable the hires_timeout_enable kernel parameter

    kctune hires_timeout_enable=1

The select(2)code has been modified to use the high resolution timer functionality. The applications which use select(2)and specify small timeouts will timeout right after the specified duration and this will reduce the long wait time. With this higher resolution, the timer API interfaces can support time intervals less than the current 10 ms. The hires_timeout_enable parameter changes take effect immediately. So it can be done while the server is up and running.

SQL iDataAgent

You can improve the performance of backup and restore operations by modifying the following parameters for SQL iDataAgent:

Parameter Default Value Supported Value
maximum size of data blocks used during backups 65536 Bytes 512 Bytes to 65536 Bytes
number of buffers used to reserve bandwidth for data transfer 20 1,2,3
maximum amount of data to be transferred at a time during backups 2097152 Bytes 65536 Bytes to 4194304 Bytes

For more information on how to setup these parameters, refer to Enhancing Performance During Backups.

Exchange iDataAgent

Exchange Mailbox data movement operations are constrained by the Microsoft MAPI API which limits data movement operations to an average of 2GB per hour per stream. This mode of data movement actually logs into each mailbox and scans each piece of mail as it is delivered to the Inbox.

You can improve the performance of data movement operations by creating multiple subclients. This will enable parallel data movement operations. However, the cumulative throughput of the Exchange server may decrease if sufficient system resources are not available. Therefore create user-defined subclients to divide mailbox backups into groups based on specific criteria. For more information, refer to Grouping Mailboxes Into User-Defined Subclients.

Image Level iDataAgent

You can optimize the performance of data movement operations using the following methods:

Defragmenting the Disk

If a disk backed up by the Image Level agent is highly fragmented, the size of the backup will be significantly larger than the valid data on the client computer. This will increase the time required for data movement operation and also consume more space on the storage media.

Configuring the Disk Extent Size Parameter for Windows

The Image Level iDataAgent backs up extents on the source drive. The default value is 512KB. You can change the disk extent size to improve the performance of data movement operations. The supported values are 64KB, 128KB, 256KB, 512KB and 1 MB. The value must be power of 2.

Consider the size of the volume to be protected by the Image Level iDataAgent relative to the size of the extent to be used. For example, a 512KB extent setting against a backup of 10KB of data is backed up entirely, including all of the empty blocks of data (502KB of data).

For more information, refer to Change the extent size for Backup Applications.

When you are changing the extent size, keep in mind that:

  • Backup extent size must be uniform across source and destination computers and not larger than the size of the source volume.
  • In a clustered environment, all of the physical nodes must have the same Backup extent size.
  • Once the disk extent size is reconfigured any incremental and differential backups completed prior to the reconfiguration are lost. The next data movement operation will be converted to a FULL.
  • You must restart the client after changing the extent size.

Configuring the Disk Extent Size Parameter for Unix

The Image Level iDataAgent backs up extents on the source drive. The default value is 2MB (4096 X 512 bytes). You can change the disk extent size to improve the performance of data movement operations. The supported values are 128, 256, 512, 1024, 2048, 4096, 8192, 16384, 32768, etc.  The value must be power of 2.

Consider the size of the volume to be protected by the Image Level iDataAgent relative to the size of the extent to be used. For example, a 512KB extent setting against a backup of 10KB of data is backed up entirely, including all of the empty blocks of data (502KB of data).

You can change the Disk Extent Size while configuring the CXBF device. For more information, refer to Configure a CXBF Device in Volume Explorer.

You can also use the following additional setting to change the disk extent size:

Additional Setting Location Supported Values
DsnapChunkSize /etc/CommVaultRegistry/Galaxy/Instance<xxx>/UnixImageIDA/.properties 128, 256, 512, 1024, 2048, 4096, 8192, 16384, 32768, etc.  The value must be power of 2.

When you are changing the extent size, keep in mind that:

  • Backup extent size must be uniform across source and destination computers and not larger than the size of the source volume.
  • In a clustered environment, all of the physical nodes must have the same Backup extent size.
  • For Image Level backups for Linux or Solaris client servers, the extent size can only be changed when the CXBF device is configured. To modify the extent size of an existing CXBF device, the server administrator should first de-configure the CXBF device and reconfigure with the new extent size.
  • If the source volume has high levels of disk fragmentation or small average file sizes, use lower values extent size.
  • Once the CXBF device is reconfigured any incremental and differential backups completed prior to the reconfiguration are lost. The next data movement operation will be converted to a FULL.

Oracle iDataAgent

You can improve the performance of backup and restore operations by modifying the following parameters for Oracle iDataAgent:

Parameter Default Value Description
Number of data files and archive files to be included in each RMAN backup set 32 Increase the value of this parameter for faster backups. However, increasing the value in this parameter will create additional CPU overhead in order to optimize the population of the Archive file.  The granular restore of individual table spaces and data files will be slower.
Number of open data files that can be read by RMAN during the backup 8 Reduce the value of this parameter for faster backup and less system load on the Oracle server.
Buffer size used by Oracle agent to transfer data to a storage media 262144 KB Increase the value of this parameter for faster tape drives or disk libraries.

For Example: For SDLT or LTO tape drives, a minimum value of 1048576 (1MB) is recommended.

For more information on how to setup these parameters, refer to Enhancing Backup Performance.

Also, if you are experiencing performance issues during backup, you can troubleshoot them by enabling logging of performance details in the log files. These performance counters contain information that help in resolving the performance related issues during backups. See Troubleshooting Performance Issues for more information.

Informix iDataAgent

You can optimize the performance by modifying the following parameters for Informix iDataAgent:

Adjusting Buffer Size

You can modify the buffer size settings using the BAR_XFER_BUF_SIZE parameter in the $ONCONFIF file on the database server. For best performance of data movement operations set the value to 30.

Configuring On-Bar Parameters

You can also configure the following parameters on the Informix database server:

Parameter Description
BAR_IDLE_TIMEOUT This parameter specifies the maximum number of minutes that an ON-Bar worker process is idle before it is shut down.
BAR_MAX_BACKUP This parameter specifies the maximum number of backup processes per ON–Bar command. You can control parallel execution of ON–Bar processes using this configuration parameter.
BAR_NB_XPORT_COUNT This parameter specifies the number of shared-memory data buffers for each backup or restore process.
BAR_PROGRESS_FREQ This parameter specifies how frequently the backup or restore progress messages display in the activity log.
LTAPEBLK This parameter specifies the block size for logical-log backups made with ontape, onload, onunload.
LTAPEDEV This parameter specifies the tape device used for logical-log backups made with ontape.
TAPESIZE This parameter specifies tape size for logical-log backups made with ontape.

DB2 iDataAgent

The following options are available for enhancing the backup performance and reducing the network bandwidth used for performing the backups.

  • The number of streams
  • The buffer size
  • The buffer number
  • Parallelism

The configured values have a direct impact on the DB2 performance. The DB2 client computer must also be considered when you assign values to these parameters.

When you set the values to a higher number, the operations use more of the client computer memory. The performance is reduced on computers that cannot handle higher memory usage.

Specifying the Number of Streams (Open n Sessions)

If specified, the backup process will open n number of I/O sessions to the SnapProtect MediaAgent to send the data to storage media.

The number of sessions is limited by the number of streams configured at the storage policy level. If the tape drives are not available at SnapProtect media library when a backup is directed to the tape storage pool, some of the sessions will have to wait until the tape mounts are free and available again.

Specifying the Number of Buffers for the Backups

When you backup the database to multiple locations, you can give sufficient buffer value to improve the backup performance. The default value is 2.

The number of buffers should be:

#sessions + #parallelism +2.

Also, the following calculation must fit:

(number of buffers * buffer-size) < UTIL_HEAP_SZ (UTIL_HEAP_SZ is the database utility heap size).

Specifying the Buffer Size

You can specify the size (in 4 KB pages) of each buffer to be used for building the backup image. This value is used as the buffer allocation size in pages (4 KB) when you build the backup image.

This value is used as the buffer allocation size in pages (4 KB) when you build the backup image. When backing up a database, the data is first copied to an internal buffer. Data is then written from this buffer to the backup media when the buffer is full. Tuning BACKBUFSZ can help improve the performance of the SnapProtect backup utility as well as minimize the impact on the performance of other concurrent database operations.

Use a buffer size that is a multiple of the extent size. If multiple table spaces have different extent sizes, the buffer size value must be a multiple of the largest extent size.

Configuring the Parallelism for Backups and Restores

Note: If you use deduplication, set the Parallelism value to 0.

If the DB2 database contains large number of tablespaces and indexes, you can perform backups and restores faster when you set a maximum number of concurrent parallelism queries to take advantage of available Input/Output bandwidth and processor power of DB2 server. DB2's query parallelism targets Input/Output intensive queries for example, tablespace scans, large index scans etc.) and CPU intensive queries (for example, joins, sorts, complex expressions etc.). If the number is not set, the optimal value is automatically chosen. When you set this parameter, it can reduce the time required to complete the backup (specially, if the backup is going to a disk).

This parameter defines the number (n) of processes that are started to read the data from the database. A specific table space is assigned to backup as part of each process. When it completes the tablespace backup, it requests another.  If you are trying to backup to different targets (for example, using multiple sessions to send the data), parallelism should not be greater than the number of targets (sessions).

NetApp NDMP File Server

You can improve the performance of data movement operation for NDMP and NRS clients using the following guidelines:

  • Turn off the File History on the appliance.
  • Ensure that the MediaAgent managing NDMP operations does not reside on the CommServe.
  • Ensure that multiple data streams are used for data transfer to the MediaAgent.
  • If the tape is attached to a NAS client, the indexing operation is completed on the MediaAgent. Ensure that the MediaAgent has sufficient memory available for indexing.
  • Use the syssat command to review the CPU consumption.
  • When the backup is running, use the following command to fetch information about MediaAgent performance:

    netstat -a

    The send_q information will determine whether network queues are becoming full.

Tuning the Performance of NetApp as a Disk Library

Follow the guidelines given below to improve the performance of the NetApp Disk Library:

  • Do not fill an aggregate more than 90% of capacity, as there is a sharp decline in performance when an aggregate is too full.
  • Configure backup volumes or LUNs with 0% fractional reserve, 0% snap reserve, and snapshots disabled. Refer to NetApp Support TR 3348 for descriptions associated with each of these settings: http://media.netapp.com/documents/tr-3348.pdf
  • When you are configuring a large disk library, maintain individual LUN sizes in 4-8 TB range. You can scale down if only a small TB footprint will be used for storage on disk.
  • If you are using iSCSI LUNs and not Fiber Channel ones, refer to NetApp Support technical report 3749 for additional background: http://media.netapp.com/documents/tr-3749.pdf . This report provides information regarding NetApp performance and LAN configuration that can help you with the CommVault MediaAgent configuration.
  • Do not Thin provision LUNs or Volumes that are disk library mount points. This increases the write overhead on the NetApp appliance. When backups are running, the controllers are allocating space for the volume at the same time as the write operations are occurring.

Improving Performance of NetApp Restore Operations

Follow the guideline given below to improve performance of restore operations for NetApp File Server:

  • Before performing the Direct Access Restore, refer to FAQs for NAS iDataAgent.
  • Create multiple subclients before performing the backup.
  • Do not use the nRESTORELIMIT additional setting to improve the performance of restore operation for NetApp File Server. When you are restoring a single directory, the list of items to restore contains one entry. The nRESTORELIMIT is used to change the number of items sent in each restore request. The default value is 8192 entries. Therefore, unless the you select more than 8192 items for restore there is no need to use the nRESTORELIMIT key.

Auxiliary Copy

You can improve the performance of Auxiliary Copy operations using the following guidelines:

Configuring an Alert

The Auxiliary copy operation enables you to create a secondary copies of data associated with a storage policy. When the data to be copied exceeds a specific threshold or if the data is not copied for specific number of days, you can receive a notification. Once you receive the notification, you can optimize and troubleshoot the auxiliary copy operation.

You can enable an alert to receive the notification and set the thresholds. For more information, refer to Auxiliary Copy - Alert.

Optimizing the Auxiliary Copy Operation for Disk

Optimizing the Auxiliary Copy Operation for Tapes

  • Validate the drives before performing any backup operation. For more information, refer to Validating Drives in a Library.
  • Check if the software and hardware compression is enabled for the jobs to be copied. For more information, refer to Data Compression.
  • Review the Auxiliary Copy logs to determine if the same media is mounted multiple times.

Optimizing Data Movement Performance for the Encrypted Data

The encrypted data movement operation is always slower than an unencrypted data movement operation. The software based encryption consumes CPU resources. Therefore, it is recommended to perform the encryption of the data on the system that has the maximum CPU resources available.

You can select the method of encryption from several algorithms and key length options. For more information about Configuration options, refer to Data Encryption.

It is recommended to select specific data from a client for encryption, instead of performing bulk encryption for the client. Do not encrypt Windows executable and programs and similar object types.

Cloud Connection Performance Tuning

If the cloud connectivity is through a  high-speed network of about 1 GB per second or higher, follow these recommendations to get the maximum performance for the cloud-based backup and restore. If you have upgraded to Service Pack 11 or higher, the additional settings are enabled by default.

Note:

These settings consume large amounts of memory on the MediaAgents. Therefore, we do not recommend these settings for low-speed networks.

  • Check that Cloud performance-specific additional settings are set correctly on the MediaAgent. Check the list below for Backup and Restore.
  • Check the Storage Policy copy > Data Path property > set Chunk size to 2 GB.
  • Check the Storage Policy copy > Data Path property > Set Block size to 1024 Kb.
  • Check that the Number of Streams is set to 10 or higher in the Storage Policy properties.
  • Check the Subclient property > Number of Data Readers are set to a higher value (for example, 10) and select the Allow multiple data readers within a drive or mount point check box.

Backup Jobs

Enabling or Disabling the Temp File for Upload

Value 0 is for memory buffer.

  1. From the CommCell Console, navigate to Storage Resources | MediaAgents.
  2. Right-click the appropriate MediaAgent, and then click Properties.
  3. Click the Additional Settings tab.
  4. Click Add.

    The Add Additional Settings dialog box appears.

  5. In the Name box, type nCloudUseTempFile.
  6. In the Value box, type 0.
  7. Click OK.

Setting the Maximum Number of Concurrent Upload Threads Per Stream

  1. From the CommCell Console, navigate to Storage Resources | MediaAgents.
  2. Right-click the appropriate MediaAgent, and then click Properties.
  3. Click the Additional Settings tab.
  4. Click Add.

    The Add Additional Settings dialog box appears.

  5. In the Name box, type nCloudNumOfUploadThreads.
  6. In the Value box, type 3.
  7. Click OK.

Setting the Size of the Subfile to Upload to a Cloud Server

  1. From the CommCell Console, navigate to Storage Resources | MediaAgents.
  2. Right-click the appropriate MediaAgent, and then click Properties.
  3. Click the Additional Settings tab.
  4. Click Add.

    The Add Additional Settings dialog box appears.

  5. In the Name box, type nCloudMaxSubFileSizeKB.
  6. In the Value box, type 32768.
  7. Click OK.

Improving the Speed of Uploading Data to a Cloud Server

Default value is 0.

  1. From the CommCell Console, navigate to Storage Resources | MediaAgents.
  2. Right-click the appropriate MediaAgent, and then click Properties.
  3. Click the Additional Settings tab.
  4. Click Add.

    The Add Additional Settings dialog box appears.

  5. In the Name box, type nCloudSocketSendBufferBytes.
  6. In the Value box, type 1048576.
  7. Click OK.

Restore Jobs

Enabling or Disabling the Temp File for Downloads

Value 0 is for memory buffer.

  1. From the CommCell Console, navigate to Storage Resources | MediaAgents.
  2. Right-click the appropriate MediaAgent, and then click Properties.
  3. Click the Additional Settings tab.
  4. Click Add.

    The Add Additional Settings dialog box appears.

  5. In the Name box, type nCloudUseTempFile.
  6. In the Value box, type 0.
  7. Click OK.

Setting the Number of Read Ahead Threads

Default value is 0, not to read ahead.

  1. From the CommCell Console, navigate to Storage Resources | MediaAgents.
  2. Right-click the appropriate MediaAgent, and then click Properties.
  3. Click the Additional Settings tab.
  4. Click Add.

    The Add Additional Settings dialog box appears.

  5. In the Name box, type nCloudNumOfReadAheadThreads.
  6. In the Value box, type 2.
  7. Click OK.

Setting the Number of Read Ahead Files

Default value is 0, not to read ahead. Minimum value should be at least 1.

  1. From the CommCell Console, navigate to Storage Resources | MediaAgents.
  2. Right-click the appropriate MediaAgent, and then click Properties.
  3. Click the Additional Settings tab.
  4. Click Add.

    The Add Additional Settings dialog box appears.

  5. In the Name box, type nCloudNumOfReadAheadFiles.
  6. In the Value box, type 4.
  7. Click OK.

Improving Speed of Downloading Data from a Cloud Server

Default value is 0.

  1. From the CommCell Console, navigate to Storage Resources | MediaAgents.
  2. Right-click the appropriate MediaAgent, and then click Properties.
  3. Click the Additional Settings tab.
  4. Click Add.

    The Add Additional Settings dialog box appears.

  5. In the Name box, type nCloudSocketReceiveBufferBytes.
  6. In the Value box, type 1048576.
  7. Click OK.

Tuning the Performance of 10GB Ethernet Environment

Follow the guidelines given below to improve the performance of data movement in a 10GB Ethernet environment: