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ONTAP Snapshot for ContinuousDataReplicator

Table of Contents

Overview

The ONTAP Snapshot is used to create Recovery Point snapshots of a destination. The destinations are UNC path, iSCSI LUNs to a NetApp file server in case of Windows and a mounted NFS export in case of Unix.

Configuration

The following must be done before using ONTAP Snapshot.

  1. Verify System Requirements -- The source and destination computers must meet the System Requirements, and have a supported operating system platform and application server software for using ONTAP Snapshot with ContinuousDataReplicator (CDR). Refer to ContinuousDataReplicator -- Application Support and Snapshot Engines - Support.
  2. Install the Software -- Install CDR software on the source and destination computer(s). For instructions, see Deployment - ContinuousDataReplicator.
  3. Configure the Agent -- For Unix, right-click the Agent and select Properties. In the Authentication tab, click Filer Management. From the Array management dialog box, add the credentials for the user account to be used when using ONTAP snapshots.

    Ensure that you provide the fully qualified domain name or TCP/IP address of the filer in the Control Device ID field.

  4. Configure the Replication Set -- For Windows, for a destination computer to use ONTAP Snapshot to create Recovery Points, right-click the Replication Set on the source computer and select Properties. In the Replication Options tab, select ONTAP in the Select Snap Engine Type for Recovery Point Creation section. To access the filer, specify user account information in the General tab of the replication set properties on the source computer. For Unix, the Snapshot engine is automatically selected based on your destination.

    For Fan-In Recovery Points on Windows, right-click the ContinuousDataReplicator Agent on the destination computer and select Properties. In the Fan-In tab, click Recovery Points tab and select Use ONTAP snapshot for ONTAP LUN destinations option, to create ONTAP snapshots on iSCSI LUN. If your destination is NetApp filer and destination path is UNC path, ONTAP Snapshot engine is automatically selected.

    To access the filer, you must specify the user credential details as follows:

    • For Recovery Points, from the General tab of the replication set properties on the source computer, specify the credentials for the user account to be used when using ONTAP snapshots.
    • For Fan-In Recovery Points, from the General tab of the agent properties on the destination computer, specify the credentials for the user account to be used when using ONTAP snapshots.

For more information about configuring, creating, and using Recovery Points with CDR, see Recovery Points.

Backing up Data from ONTAP Snapshots

Recovery Points created using ONTAP Snapshot can be backed up. For more information about performing backups of Recovery Points, see Backups of Recovery Points.

For information on restoring data that was backed up using ONTAP Snapshot, see Restore Data - ONTAP Snapshot.

Recovering Data from ONTAP Snapshot

Data from Recovery Points created using ONTAP Snapshots can be recovered in a variety of ways. For information on recovering data from ONTAP Snapshot, see Recover Replicated Data.

Considerations

Before using CDR with ONTAP Snapshot, review the following information:

General

Consider the following, if snapshots are created when a LUN is cloned:
  • Delete snaps in the reverse order they were created in. If you have a situation where the busy snap is no longer mounted but is still shown as busy, then all additional snaps on this volume created while that snap was mounted will need to be deleted so that this snap will no longer be busy. See the ONTAP 7.3 note below to avoid this dependency.
  • Do not mount a volume and create another snap for the volume. To avoid this snapshot dependency, do not manually create a snapshot of a volume while you have a snapshot mounted.

For NetApp ONTAP version 7.3, there is an option to enable the system to only lock backing Snapshot copies for the active LUN clone. If you do this, when you delete the active LUN clone, you can delete the base Snapshot copy without having to first delete all of the more recent backing Snapshot copies.

This behavior in not enabled by default; use the snapshot_clone_dependency volume option to enable it. If this option is disabled, you will still be required to delete all subsequent Snapshot copies before deleting the base Snapshot copy.

We recommend that  you enable this option but if you are using any other applications on the LUN, review the documentation for this feature for other impacts. As with this option enabled, if you delete the snapshot that had originally cloned the LUN, then you cannot use “snap restore” to restore the clone from one of the later snaps. If this volume options is later turned off on the volume, then you may have difficulties deleting snapshots because the dependencies will again be enforced.

iSCSI LUN

CDR on Windows supports iSCSI LUNs as destination for NetApp filers. When iSCSI LUN is used as destination to create Recovery Points, you must specify user authentication details. The user information must be specified either in the General tab of the replication set properties on the source or in the General tab of the agent properties on the destination.

The user should have permission to access the filer.

Windows

  • One snapshot is created per CIFS share. If E: is mapped to \\me\CDR_1 and D: is mapped to \\me\CDR_2, there will be two snapshots created on the file server even if both UNC paths end up on the same volume. It may be useful, using this same example, to instead map D: to \\me\CDR_1\D and E: to \\me\CDR_1\E, so that only 1 snapshot is needed.
  • Snapshots on the NetApp file server will be named cvcdr_<timestamp>_<number> , for example cvcdr_1189118004_1. If there are multiple shares used, then one snapshot will be created for each share and the <number> will be incremented for each. The corresponding CIFS share on the snapshot will be named 1189118004_1. This share will be in exactly the same place as the share being replicated to, meaning for example that if \\me\CDR_1 is for path /vol/myvol/dir1/dir2, then CIFS share 1189118004_1 will be on /vol/myvol/.snapshot/ cvcdr_1189118004_1/dir1/dir2.
  • NetApp file server destination should be a NTFS qtree.

Unix

  • It is recommended that you add the local mount path of the filer to the list of FS to be auto-mounted on reboot. For instance, on AIX you need to add it to /etc/filesystems file and set the Mount to true. This will ensure that if the destination machine gets rebooted, the source machine will continue to replicate to the destination path on the filer and all the CRP snapshots will be automatically mounted.
  • To avoid the creation of additional folders on the destination machine, it is recommended that you turn on the nosnapdir option on the volume. To do so, run the vol options <volname> nosnapdir command on the ONTAP console.

License Requirement

To perform a data protection operation using this Agent a specific Product License must be available in the CommServe® Server.

Review general license requirements included in License Administration. Also, View All Licenses provides step-by-step instructions on how to view the license information.