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DQ965GF poor RAID 5 write performance

Discussion in 'Intel' started by mrdanielmorgan, Dec 21, 2006.

  1. Hi

    Apologies if this is posted in the wrong group, if so could you point
    me in the right direction.

    I've just built a new home server; operating system is Server 2003 R2
    standard. Motherboard is an Intel DQ965GF with a Core2Duo 1.86 and 2GB
    DDR2 Kingston RAM.

    I've been doing some testing before posting so hopefully you'll be able
    to help me out.

    In the system I have 3x500GB Seagate SATA drives and 1x320GB Maxtor
    SATA drive. Initially I created a RAID 5 with the 3x500's. I
    partitioned that into a 30GB for the system and that left somewhere
    over 900 for the data.

    Once it was up and running I updated the drivers and then tested the
    drive performance. I used YAPT. Read performance on both partitions
    was as I had hoped, it was around 130meg/sec. Write performance on the
    data partition was 90meg/sec. However write performance on the system
    partition was only 10meg/sec. I've checked the net and can't find
    anything and I've confirmed write cache is on.

    The next thing I did was to brake the RAID and have the drives as stand
    alone. I installed Server on the 320GB maxtor and then tested
    performance. The 3 Seagates all returned consistent 72meg/sec read and
    write. The maxtor returned 62meg/sec read and write.

    I've now recreated the RAID 5 and installed Server again but all as 1
    big partition. Read performance is back up to 130's,eg/sec but write
    is still 10meg/sec.

    It's gone 1AM in the morning now but I might try XP rather than server
    tomorrow but I'm sure that will be a waste of time.

    Help

    Many Thanks

    Dan
     
    mrdanielmorgan, Dec 21, 2006
    #1
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  2. mrdanielmorgan

    Yousuf Khan Guest

    It's typical for RAID5 write performance. Also remember that this is a
    software RAID5 rather than a hardware RAID5, which makes it even worse.

    Yousuf Khan
     
    Yousuf Khan, Dec 21, 2006
    #2
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  3. Software RAID? are you sure
     
    mrdanielmorgan, Dec 21, 2006
    #3
  4. mrdanielmorgan

    Yousuf Khan Guest

    Yup, I'm afraid so. You can't call it hardware RAID unless you have a
    separate little processor doing all of the parity calculations for you.
    All motherboard RAIDs are a big rip-off, because of the parity
    calculations are being done by the main processor.

    Yousuf Khan
     
    Yousuf Khan, Dec 22, 2006
    #4
  5. * :
    Yousuf already told you that you have a software RAID, so don't expect
    miracles. But usually a software RAID is quite fast on todays processors
    if the load isn't too big (and that shouldn't be the case on a home server).

    As to your problem, I think the results you get are bogus. 130MB/s with
    three 7200rpm SATA drives in RAID5 is a bit too optimistic. I don't know
    your software but it looks that it also measures the Windows disk cache
    which is nonsense. Try another program like the ATTO disk benchmark:
    <http://members.home.nl/rvandesanden/Downloads/ATTO.rar>

    Your writing results are indeed very low. Your disk write cache is
    probably disabled, by enabling it you can increase the writing
    performance (but you loose all data in write cache if there is a power
    outage). But be aware that the writing performance of RAID5 is always
    quite limited.

    Just do a retest with the ATTO disk benchmark, set the Transfer Size to
    0.5 to 1024kb and the total Length to 32MB.

    Benjamin
     
    Benjamin Gawert, Dec 22, 2006
    #5
  6. Cheers Benjamin

    Panic over. I did a test with IOmeter

    Here are my result files:

    RAID5
    http://www.islandpcservices.co.uk/dan/misc/raid5.htm

    Standalone Maxtor
    http://www.islandpcservices.co.uk/dan/misc/maxtor.htm

    Those were with a 1gig file and 2 mins run time. The speeds with bigger
    tst files is consistent.

    The RAID has some 300gig of data on it now so the test file would have
    been created near the middle of the disc. The Maxtor only has 10gig on
    it. I'd imagine if both drives were empty the speeds would be slightly
    faster.
     
    mrdanielmorgan, Dec 22, 2006
    #6
  7. Actually a firmware RAID, but essentially all that means is that you
    have a slightly better chance of boot if you have some very unlikely
    failure modes. It's not hardware, where you hand the data to the
    controller and smile, the firmware breaks the data into chunks,
    calculates parity, and issues a separate write to each drive (and if you
    have PATA drives on the same cable that really sucks).

    Having the write size larger than the stripe size helps, particularly if
    the write is some multiple of what fits on a single trips (N-1 data
    chunks + one parity).

    RAID-5 is expensive for write.
     
    Bill Davidsen, Dec 27, 2006
    #7
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