4sysops - FREE: Iometer - measure disk performance

Iometer is a free Open Source tool to test disk performance. Among others, you can measure the I/O transfer rate and the average I/O response time. Its first version was released 10 years ago for Windows NT. But it is still a useful tool because it also works under Windows XP/2003 and even with Vista and Windows Sever 2008. Iometer supports many different settings. In this post, I will just show you how to get started with this nifty free disk measurement utility. If you like it, you should consult its manual for further instructions.

Note that you have to run this tool with administrator privileges. Under Vista, you must elevate Iometer, that is, it has to be launched explicitly “as administrator”. Iometer’s navigation pane displays the so-called workers. They contain the I/O devices, i.e. the available logical drives. Click on the disk target tab and select one of the drives. You should specify the number of sectors Iometer can use for the performance test. Otherwise it will use all available disk space. For your first test, 1000 sectors will do. Iometer creates a file called iobw.tst in the root folder of the corresponding disk for this purpose.

Next, you have to configure the Access Specifications. You can find them under the corresponding tab. I suggest you use the pre-configured “512B; 100% Read; 0% random” access specification for your first performance test. Add it to the “Assigned Access Specifications” column. Now, click on the “Results Display” tab. Change the update frequency to 3 seconds. This allows you to watch the measurement process more or less in real time.

To start the performance test, you have to click on the green flag in the task bar. Iometer will ask you to specify the name of the csv file where Iomenter will log the results of your performance test. It will then create the iobw.tst file I mentioned above. The status bar will display “Preparing drives” until Iometer is finished. Now you should be able to watch the results of your performance measurement. To display the gauge you see above, you have to click on one of the arrows next to the measured parameters. To end the test, click on the “Stop” icon in the task bar.