IOPs and Capacity Planning Guidelines for Indexing

Table of Contents


This document describes how to plan for and measure Input Output Operations per second (IOPs) when assigning space for the Index Cache.

The following section explains the use of Iometer, which is a widely used, industry standard tool for measuring IOPs. Using IOPs rating provides a standard and simplified way to commission storage without having to understand and use proprietary tools. See the Iometer website for complete reference information for this tool.

Index Cache Directory Capacity Recommendation

The index cache must be hosted on a separate volume that meets the IOPS and size requirements described in Hardware Specifications for MediaAgent.

Iometer on Windows

Setting Up and Running Iometer

A worker thread is an entity that runs the test defined on the Access Specification Tab of the Iometer User Interface. Running multiple worker threads concurrently is useful for testing performance. This section tells how to set up and run Iometer with one worker thread. Testing Index Cache Performance describes multiple worker thread set-up and testing.

  1. In Explorer, navigate to the software_installation_directory/Base folder, then right-click Iometer > Run as Administrator.
  2. In the license dialog box, click I Agree.
  3. In the Topology pane, click the name of the computer. The available disk drives appear in the Disk Targets tab.
  4. Under All Managers, expand MediaAgent_name. Iometer, on startup, creates one Manager with multiple worker threads.
  5. Leave one worker thread, but delete the remaining ones by selecting each additional worker thread, then clicking Disconnect Selected Worker or Manager .

    • We recommend running Iometer on the physical disk where the index cache is to be stored. Iometer allows physical disks to be selected only when there are no volumes on the disk.
    • If Iometer needs to be run on a volume, the volume should have at least 60% free space. For example, a 500 GB volume should have at least 300 GB free.

  6. On the Disk Targets tab, select the disk to test.

    Values for Maximum Disk Size and Starting Disk Sector should be set to 0 (zero), to test the complete disk.

    Before running a test on a volume, Iometer prepares the volume by creating the file named iobw.tst, on which it will run read/write tests.

    Blue disk icons represent physical drives that have no partitions on them.

    Yellow disk icons with a red strike-through are volumes that need to be prepared before the test. These are the volumes that do not contain the iobw.tst file.

    Yellow disk icons without the strike contain the iobw.tst file.

Access Specifications

  1. Click the Access Specifications tab.
  2. In the Global Access Specifications area, select the Iometer profile to be used for the IOPs measurement test. The profile that most closely emulates the way c-tree accesses a disk during database lookups is:

    4K Block Size, 100% Access, 100% Random, 50% Read and 50% Write

  3.  If that profile does not already exist, create one by clicking New. Click OK to add the new specification.
  4. Click the profile in the Global Access Specifications area, then click to place it in the Assigned Access Specifications area, so it will run.

Results Display

  1. Click the Results Display tab.
  2. Change the Update Frequency slider to 5 seconds.

Test Setup

  1. Click the Test Setup tab.
  2. For Run Time, enter 30 minutes.


  1. Click Start Tests to run the Iometer test.
  2. A standard Save File dialog appears. Select a file to store the test results (by default it saves as results.csv).

    After a few seconds the test results appear in the Results Display tab.

    Run the test for around 30 minutes or until the IOPs value has stabilized.

  3. Click Stop Test . The test stops and the final results are saved in the results.csv file. This can be viewed in any text editor.

    At the end of the test, note the IOPs test rating.

  4. If you are running Iometer on a volume, make sure to delete iobw.tst file after the test is complete.

Testing Index Cache Performance

Once you have successfully set up and run Iometer as described in Setting Up and Running Iometer, you can test index cache performance by creating and running eight worker threads, as follows:

  1. Click the Start a Duplicate of This Worker on This Manager button to create a duplicate worker thread with the same settings. Create a total of 8 worker threads this way.
  2. Set your test parameters and run the test as described in the sections named:
    1. Results Display
    2. Test Setup
    3. Results

Iometer on Linux

To test the disk available on a Linux computer, Iometer requires the Iometer UI and Dynamo. In this example, the Linux computer under test is running Dynamo, and the Windows host is running the Iometer UI, which reports the results.

  1. To perform an Iometer test on a Linux computer, two hosts are required:
    • A Windows host that runs the Iometer UI.
    • The Linux MediaAgent that runs Dynamo to test the disks (which can be separate from the computer being tested).

    Installation instructions for these components are in the Iometer documentation, available from the Iometer website.

  2. Verify network connectivity between the two hosts by ensuring that each machine can ping the other.
  3. Run Dynamo on the Linux MediaAgent with two parameters:
  4. -i  indicates the IP address of Windows host running the Iometer UI.

    -m  indicates the IP address of the Linux host.

    In the figure below, the Windows host is at IP address , while the Linux host is at IP address

  5. After running Dynamo, run Iometer with administrator privileges on the Windows host, as described in these sections:

    Be sure to run Dynamo on the Linux host before running Iometer on the Windows host.