RAID benchmarks

By Rick Cook

Benchmarking programs are the first step in performance testing any product. Ideally, a benchmark provides a highly standardized, vendor-neutral, apples-to-apples comparison of two products, such as storage subsystems.

When it comes to RAID systems, overall I/O performance is probably the best single measure of speed. There are a number of benchmarks that can test the I/O performance of a RAID system. They range from simple, quick-and-dirty tests you can do on-the-fly to elaborate tests that measure nearly everything about file-system performance. Since many of the programs are inexpensive shareware or freeware, it pays to have several benchmarks on-hand to use under different conditions.

Among the more popular benchmarks are:

• Iozone II. This runs under Unix, NT and DOS. It can do a fairly sophisticated analysis of file system performance.
• Disktest. This is a Unix program that can test any direct access device on the system without taking other users off-line. (However, the device being tested must be unavailable to other users.)
• IOBENCH. This benchmarking program measures fixed workload and I/O throughput performance on Unix systems.
• Qbench. This is a DOS program from Quantum Corp. that measures data access time and data transfer rate.
• Nbench. This tests a number of parameters on a Windows NT system, including disk read and write speeds.
• Ntiogen. Ntiogen is a benchmark by Symbios Logic that is a port of its IOGEN benchmark program from Linux.
• IOMETER. This program was written by Intel to test disk subsystem I/O under a controlled load on NT.

Ideally, benchmarking is only part of performance testing. It should be followed by tests using your own applications and test data that represent your environment. It is entirely possible that the products with the best performance on the benchmarks will turn in a mediocre performance on your application.

Additional resources:

• Advanced Computer and Network Corp., a RAID systems integrator, has a list of useful I/O benchmarks on its site, complete with links to download. The programs are arranged by operating system. The site is at: http://www.acnc.com/04_02.html.
• For a list of the latest tips on SearchStorage, go to: http://www.searchstorage.com/searchStorage_Tips_Page/0,1800,,00.html.

About the author: Rick Cook has been writing about mass storage since the days when the term meant an 80K floppy disk. The computers he learned on used ferrite cores and magnetic drums. For the last twenty years he has been a freelance writer specializing in storage and other computer issues.