How to find out the maximum writing speed of my hard disk?

The best way to find out the maximum writing speed of your hard disk is to run writing tests with a single large block:

• "-LS" - Sets SQLIO to report latency measurements using the system timer.
• "-kW" - Sets SQLIO to perform writing tests.
• "-i1" - Specifies the run size of 1 I/O tests Basically, SQLIO will perform only I/O test in each run.
• "-f1" - Specifies the stripe factor of 1 blocks. This option is useless now, since only 1 block is needed in each run. There will be only 1 stripe.
• "-t1" - Sets SQLIO to use 1 thread only.
• "-s300" - Sets SQLIO to run for 300 seconds, or 5 minutes.

If we run SQLIO with above options and different block sizes, we should be able to find the maximum writing speed. Here are test results on Western Digital - WD5000LPLX-08ZNT 465GB hard disk:

             Throughput   Throughput   Latency
Block Size      MBs/sec      IOs/sec        ms
----------   ----------   ----------   -------
     -b512       283.12       566.25         1
    -b1024       317.47       317.47         2
    -b2048        99.91        49.95        19
    -b4096        94.02        23.50        42

As you can see, the maximum writing speed, 317.47 MBs/sec is reached with a block size of "-b1024", or 1 MB. If the block size is too small, the operating system is not feeding the hard disk with enough data. If the block size is too big, the operating system is not able to cache it properly.

In other orders, block size of 8 MB makes a perfect match between the operating system and the hard disk.

⇒ I/O Tests on Solid State Disk (SDD)

⇐ Western Digital - WD5000LPLX-08ZNT - Maximum Reading Speed

⇑ Tuning SQLIO for Your Environment

⇑⇑ SQLIO Disk I/O Benchmark Test Tutorials