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SAS RAID5 Test Results Incorrect

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  • SAS RAID5 Test Results Incorrect

    We have several HP DL385 boxes with onboard RAID and SFF SAS drives (146GB, some 10K, some 15K).

    When doing Advanced disk benchmarking, we consistently get sequential write numbers of 2-3MB on a 6-disk array when configured with RAID 5.

    800MB test file
    16K block size
    Async with depth 20

    This 3MB number does not reflect the actual disk performance when ballparked with simple file copies. It appears to be a testing anomaly. The sequential read numbers appear to be fine (120-140MB).

    When the same drives are configured for RAID10, we get what appear to be reliable numbers (130-150MB sequential read, 100-110MB sequential write).

    Is there something in Passmark 7 advanced disk testing that is not valid for a SAS RAID5 array on HP RAID controllers?

  • #2
    We have seen numerous cases where bad device driver, or configuration settings, or RAID controller bugs caused problems.

    See these old posts as examples.
    Slow RAID 0 Performance with 74Gb 10K Raptors
    Slow write performance FastTrak S150 TX4 RAID 1
    RAID 0 bad Slowdown

    We aren't aware of any bugs in the advanced disk test.

    Doing file copies isn't the same as doing Async access. I would think file copies are issued as synchronous commands.


    • #3
      A synchronous test with the same file and block size show 1.25MB. This has to be a bug. A 128MB file copies to the drive in less than a second.


      • #4
        Try doing a file copy with a much larger file. At least as large as the amount of RAM that you have, to remove any caching effect. (e.g. 4GB+).


        • #5
          I copied three files totaling over 8GB to the volume and timed using ntimer. The overall speed was about 92MB/s. Here are the details.

          C:\cmdtools>dir 71*.*
          Volume in drive C has no label.
          Volume Serial Number is 78B5-7408
          Directory of C:\cmdtools
          04/30/2009 09:39 AM 3,270,828,032 7100.0.090421-1700_x64fre_client_en-us_Retail_Ultimate-GRC1CULXFRER_EN_DVD (2).iso
          04/30/2009 09:39 AM 3,270,828,032 7100.0.090421-1700_x64fre_client_en-us_Retail_Ultimate-GRC1CULXFRER_EN_DVD.iso
          04/30/2009 12:34 PM 2,530,975,744 7100.0.090421-1700_x86fre_client_en-us_Retail_Ultimate-GRC1CULFRER_EN_DVD.iso
          3 File(s) 9,072,631,808 bytes
          0 Dir(s) 121,596,993,536 bytes free

          C:\cmdtools>ntimer xcopy 71* e:\test
          3 File(s) copied

          ETime( 0:01:33.511 )

          Calculation: 8652 MB in 93.5 seconds is 92.5 MB/s


          • #6
            What are all the settings for the test. The access method and the R/W mix and the sequential / random mix? Also, are you are sure you are testing the right drive letter in the advanced test window?

            I did a few runs here on a RAID setup and single drives (but not RAID 5). And got the results I expected (50MB/sec to 80 MB/sec). And we have had no other customers reporting problems with this test.