When implementing storage of any kind, whether it’s directly attached to a server,connected to your network (NAS), or on its own network (SAN), it’s important to know just how well your data storage performs. If you can’t pinpoint this information, managing data storage growth is difficult.
Iometer, an open source tool, available for download from www.iometer.org, can help youidentify this critical infrastructure measure and help you make better decisions about what kind of storage you need or whether your current storage solution can handle increased load, transaction volumes and users.
Iometer actually serves an additional purpose beyond just measuring I/O performance—it can also generate the workload that is used to test the system (this component is called Dynamo). Dyanamo can be configured in a number of ways that allows very granular testing to take place so that it can test multiple scenarios. TheD ynamo component must be installed on each system for which you would like togather performance results.
Iometer and Dynamo can be installed on the sames ystem in cases where you want to test the data storage performance test tools
of the local disk system.
Installing and running Iometer and Dynamo
The Iometer installation under Windows couldn’t be any easier. Simply double-click the downloaded file and accept all of the default options. This installs Iometer onto your system and places a shortcut on your Start Menu.
Iometer is extraordinarily versatile, and the Users Guide is more than 80 pages long. However, a brief overview of some basic configurations and explaination of how to run tests locally.
For a local test, just start Iometer on the machine to which you installed the program. In Figure A below, see the Topologysection at the left. In that section you see BASE2K3, which is the name of themachine (also called a “manager” in Iometer-speak) on which Iometeris running, and Worker 1. A worker is an individual thread run by Dynamo (whichis started automatically when you run Iometer). At the right, the default tab is the Disk Targets tab, which lists the drives that are available to use for tests.
| Figure A |
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| Iometer main window – disk targets |
For anyIometer test, you must select access specifications from the AccessSpecifications tab inFigure B. The information on this tab specifies the type of IOoperations that will be performed by Iometer, allowing you to customize tests foryour particular application. This example runs tests with 512-byte and 32-KBchunks of data, with read frequency assumptions of 50 percent and 25 percent,respectively. You can customize these assumptions by clicking the New or Editbuttons and creating your own.
| Figure B |
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| Access specifications control exactly how tests run |
Before yourun your test, you can also change other parameters, such as the length of thetest. For example, if you want to get a true average reading of your disksystem performance, you might want to run the test for hours instead of secondsto guard against running the test at the same time a user is pulling a largefile from the system. Many test parameters can be adjusted by using the TestSetup tab, shown below in Figure C.
| Figure C |
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| The test setup tab provides a place to change overall test parameters |
Once youconfigure your test, click the green flag on the menu bar to start thingsrunning. Click the Results Display tab to get a real-time view of your runningtest. A sample results display is shown below in Figure D. You can expand a particular result into its own screen bypressing the right-arrow at the right of each test, which results in a screen similar to the one shown in Figure E.
| Figure D |
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| The Result Display tab provides quick access to a lot of information |
| Figure E |
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| Drill down into individual results |
This tip is intended to be a very basic introduction to Iometer, a tool that can help you get a measure for your storage system’s performance.
