How to measure disk write and read capabilities in Windows

First you need to make sure disk counters are enabled on your system. To do this, open a command prompt ant type the command diskperf and press enter. If the disk counters are enabled you should get a message saying they are either enabled, or automatically enabled on demand.

To enable all disk counters, use command prompt with the diskperf -y command. If you wish to disable the disk counters again after testing, you can do this with diskperf -n .

Now to start measuring your write speed, open Performance Monitor (from Start > Administrative tools).

To save the Performance date to a log file you need to set up a Data Collector set. To do this, expand the Data Collector Sets category in the left hand pane, and select User defined. From the Action menu, select New > Data Collector Set.

The wizard will guide you through a generic setup of Data Collector sets, but for our purpose here, you should select to create manually to getonly the data sets we are interested in.

When selecting what data to include, select at least Performance Counters. The counters to choose are under the two categories Logical Disk and Physical Disk, and will be named:

For disk write capabilities:
Avg. Disk Bytes/Write
Avg. Disk sec/Write
Disk Write Bytes/sec
Disk Writes/sec

For disk read capabilities:
Avg. Disk Bytes/Read
Avg. Disk sec/Read
Disk Read Bytes/sec
Disk Read/sec

Including Avg. Disk Queue Length can also help indicate any potential problems.

When you have completed the Wizard, select the Data Collector Set you just crated and start it from the menu bar on top or the Action menu.

Leave the data collection running for a period of time. The longer, the better in most instances. To see your drive performance during normal operation, you can collect data during any normal operating period. If you want to test it under load, you should copy a large amount of data to the drives. Note the time you are doing this so it's easier to find in the logs. When you think you have enough data, you can stop the data gathering from the top menu bar or the Action menu. The log file can now be found in the location you specified while setting up the Data Collector Set as a .blg file. Double-click this file to open it for analysis.

If you wish to monitor the system in real time, select the Performance Monitor in the left navigation pane and add the same counters as above. Note that this will only give you live information of the last minute or so, and data will not be saved if you are not running a Data Set Collector.