Implementing Sqlhdtst

Sqlhdtst can be run either by clicking on its icon or from the command prompt. This version of Sqlhdtst accepts command-prompt arguments, making it easier to run the utility from command files that fire off several simultaneous instances of Sqlhdtst.

Usage

When you run Sqlhdtst from the command prompt, it accepts the following options:

sqlhdtst [/Dtestfile] [/Ssize] [/Iiterations] [/Wnmbrwrites] [/Tthreads] [/Mmaxasync] [/Qthreadasync] [/Ooutfile] [/Bboost] [/Rreadaheadthreads] [/Ereadaheadextents]

where:

/Dtestfile

Is the full path to the file that Sqlhdtst will create for testing.

/Ssize

Is the size of the test file, specified in 2K pages.

/Iiterations

Is the number of test iterations to run.

/Wnmbrwrites

Is the number of writes to make in each iteration.

/Tthreads

Is the number of threads to use.

/Mmaxasync

Is the maximum number of asynchronous I/Os to have outstanding at any time.

/Qthreadasync

Is the maximum number of asynchronous I/Os any individual thread can have outstanding at any time.

/Ooutfile

Is the name of a file to hold an output report.

/Bboost

Indicates whether or not Sqlhdtst should run with boost priority on (1) or off (0). The default is off (0).

/Rreadaheadthreads

Is the number of readahead threads Sqlhdtst should use.

/Ereadaheadextents

Is the number of readahead extents each readahead thread should use.

When you run Sqlhdtst from an icon, you use a dialog box to fill in the above parameters. The dialog box appears when you click DiskTest/Run Test.

Remarks

If an error is detected, contact your system support provider.

If Sqlhdtst runs without reporting any errors, this does not mean the system is free of problems. It simply means Sqlhdtst did not encounter a problem. Problems could still exist that were not triggered by Sqlhdtst.

For meaningful results, run Sqlhdtst as follows:

Run at least four simultaneous instances of the program. Each instance will need to specify a unique file name.
Use a large file size. What constitutes a large file varies depending on your server and available free disk space. Try to use test files more than 50 MB in size, use much larger files when the space is available.
If you have multiple drives and/or disk controllers, ensure that at least one instance of Sqlhdtst places its file on each one.
While the disk tests are running, also run at least one instance, and preferably more, against network-based drives. For example, use as the test file path:

\\servername\c$\ftest.fil

where servername is the name of a network file server to which the Windows NT box being tested has access.

At a minimum, run the test overnight. Running the test for a few days, such as over a weekend, is best. Adjust parameters to ensure the test will run for the entire test period.
Because of the high resource load Sqlhdtst places on the system, you should not have the system in production nor be running SQL Server.
Because of the high CPU load Sqlhdtst places on the system, you may want to start Sqlhdtst from the command prompt, running in the IDLE priority class. This will not reduce the effectiveness of the test; however, it will help prevent the test from dominating the system to the point where a command session is unresponsive. For example:

start /low sqlhdtst

The test is also usually run without boost priority enabled.

When running Sqlhdtst from an icon, the dialog box presents small, medium, and large options to quickly configure tests. Using medium is a good choice for small server machines; this uses a 100 MB test file.
To effectively test a large server, use conditions such as:
- Run at least four simultaneous instances of Sqlhdtst for the disk subsystem.
- Concurrently run at least two instances of Sqlhdtst against network-based drives on a remote file server, if possible.
- Start each instance using the START /LOW command.
- Select a nonconflicting file name for each test file.
- Place a separate test file on each disk or disk controller.
- Select a file size greater than 100 MB. Make file sizes as large as possible.
- For Number of Iterations of the test, select 2000.
- For Number of Random Writes/iteration, select 10000.
- For Number of Worker Threads, select 50.
- For Max Async IO, select 255.
- For Max Async IO per Thread, select 4.

Samples

To run a single test on a small server:

start /LOW sqlhdtst /Dc:\sqlhdtst\testfile.dat /S512 /I20 /W20 /T5 /M20 /Q4 /R3 /E3

To run a single test on a medium server:

start /LOW sqlhdtst /Dc:\sqlhdtst\testfile.dat /S51200 /I100 /W500 /T25 /M20 /Q4 /R6 /E6

To run a single test on a large server:

start /LOW sqlhdtst /Dc:\sqlhdtst\testfile.dat /S512000 /I2000 /W10000 /T100 /M20 /Q4 /R12 /E12

To seriously stress test a large server that has c:, d:, e:, and f: physical disk drives:

start /LOW sqlhdtst /Dc:\testfil1.dat /S512000 /I2000 /W10000 /T100 /M20 /Q4 /R12 /E12
start /LOW sqlhdtst /Dd:\testfil2.dat /S512000 /I2000 /W10000 /T100 /M20 /Q4 /R12 /E12
start /LOW sqlhdtst /De:\testfil3.dat /S512000 /I2000 /W10000 /T100 /M20 /Q4 /R12 /E12
start /LOW sqlhdtst /Df:\testfil4.dat /S512000 /I2000 /W10000 /T100 /M20 /Q4 /R12 /E12
start /LOW sqlhdtst /D\\FileSrvr1\sharenm\testfil5.dat /S512000 /I2000 /W10000 /T100 /M20 /Q4 /R12 /E12
start /LOW sqlhdtst /D\\FileSrvr2\sharenm\testfil5.dat /S512000 /I2000 /W10000 /T100 /M20 /Q4 /R12 /E12