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Thread: DSS on ESXi 4.1 - Slow RAID5 Reads?

  1. #1

    Default DSS on ESXi 4.1 - Slow RAID5 Reads?

    Hi folks,

    I'm running DSS v6 (lite) as a VM on ESXi 4.1.

    Setup is as follows:
    2x3GHz Xeons
    12GB RAM
    PERC 5i:
    2x500gb SATA for VM Datastore's, RAID0, no read ahead, write back, 64kb block
    3x1TB SATA RAID5, no read ahead, write back, 64k block

    I've created a VM for DSS with the settings:
    1 GB RAM
    LSI Parallel:
    8gb HD (installed to)

    First, I tried formatting the datastore with an 8mb block size, and created a virtual hard drive of 1.8TB.

    Results were:
    50MB/sec write
    3/4MB read

    Next, I tried creating a datastore with a 1MB block size, created and added 8 256GB virtual hard drives under a software RAID0 array.

    Results:
    50MB/sec write
    15MB read

    Hmmmmmmmmmmmmmmmmmm

    Any ideas on whats causing the slow reads?

  2. #2

    Default

    File Copy results were done from a local client on a GB LAN.

  3. #3
    Join Date
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    Default

    test with WB(writeback) off, and report back results.

  4. #4

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    Actually I would test with it on for the LUN, also are you using Block IO or File IO?
    All the best,

    Todd Maxwell


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  5. #5

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    I'm going to try using raw disk mapping as it looks to be a better way to present DSS with the array (since the LUN im carving from is local).

  6. #6

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    Quote Originally Posted by To-M
    Actually I would test with it on for the LUN, also are you using Block IO or File IO?
    This was just a simple test using SMB/CIFS share through a Windows 7 client (management box). Not sure how to set IO options (if they are available for this type of share?)

  7. #7
    Join Date
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    Quote Originally Posted by npusnik
    I'm going to try using raw disk mapping as it looks to be a better way to present DSS with the array (since the LUN im carving from is local).
    misread your post....WB on RAID....
    like 'To' says... try it on for the LUN.

  8. #8

    Default

    Update:

    Re-initialized the arrays, gave DSS raw access to the 1.8TB array - both virtual and physical RDM methods.

    Results:
    Write, 60-70MB/sec
    Read 20MB/sec

    I only have the option for Write Through or Write Back - and I'm not sure why those would effect reading from the LUN - but I'll change it next and see what the results are.

  9. #9

    Default

    Another update:
    Created an ISCSI volume using FILE I/O, mapped the target to my Win 7 management desktop

    Results
    100MB/Sec write
    20MB/Sec read

    I'm going to try to install Dell's OpenManager to see if there's something I'm not catching with the PERC's RAID5 array.

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