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ensnare
Asked: 2011-04-18 09:25:00 +0800 CST

Poor read performance on Dell Perc H200 RAID10 with (4) 1TB 7200rpm 64MB drives

  • 772

I am seeing only 50MB/s reads:

ensnare@box:~$ sudo hdparm -tT /dev/sda
[sudo] password for ensnare:

/dev/sda:
 Timing cached reads:   4592 MB in  2.00 seconds = 2296.48 MB/sec
 Timing buffered disk reads:  192 MB in  3.90 seconds =  49.24 MB/sec

The array is already rebuilt and operational. Is this kind of slow performance normal? Anything I can do to make it faster? There weren't too many options in the controller configuration. Thanks.

dell raid hardware-raid dell-perc

6 Answers

  1. Best Answer

    The short answer is yes, that's the level of performance you should expect to see from the H200.

    The long answer: The H200 is the old SAS 6iR with SATA 6Gb/s support. It doesn't have the usual features you'd see on a RAID card (battery backup unit, onboard caching, RAID5/6 support). The cache determines how fast your RAID array is (along w/ the # of spindles and type of drive), so no cache = slow performance. Add the 7200RPM SATA drives (which are slow compared to a 10-15k RPM SAS drive) and that's the level of performance you can expect.

    • 8

  2. Please take a look at the following info:

    The default cache policy on a physical disk is Enabled in SATA drives and Disabled on SAS drives. When physical disk caching is Enabled, disk I/O performance is improved, but a power outage or equipment failure might result in data loss or corruption.

    NOTE: It is recommended that you use a backup power source for all Dell production systems.

    On a PERC H200 card, caching is forced to be disabled for all physical disks configured into a virtual disk, regardless of the drive type and default drive settings.”

    http://support.dell.com/support/edocs/storage/storlink/h200/en/ug/html/features.htm

    • 3

  3. Maybe change the stripe size, depending on what your storing.
    Is cache turned off? I have 4 1TB Western Digital Enterprise 7200 RPM drives on a 3Ware 95500-SX and my hdparm results are

    zeus:/home/Kendall # hdparm -tT /dev/sdb

/dev/sdb:
Timing cached reads:   1262 MB in  2.00 seconds = 630.86 MB/sec
Timing buffered disk reads:  128 MB in  3.03 seconds =  42.30 MB/sec

    That's my development server, though, which is under some load. I'd expect higher numbers if the array was idle, like I suspect yours is.

    Just for some perspective, I don't exactly know if your buffered reads are "slow" but I put mine up for comparison.

    • 1

  4. It seems there may be a potential "fix" here but I have not tried it myself:

    http://blog.slucas.fr/en/tips/esxi-perc-h200-slow

    • 1

  5. The H200 controller disables all disk caching built into the drives by default.

    If the server has battery backup you can enable basic drive caching on the Logical Volumes without risk.

    Goto www.LSI.com (The controller is made by LSI) and download and install MegaRAID Storage Manager.

    Highlight the Virtual Raid Volume, right click, properties. Enable Cache and save.

    You have to do this on every logical raid volume.

    Your performance difference is incredible.

    • 1

  6. Here's THE best solution if going to a H700 isnt possible. Enable cache directly from the firmware. YOU MUST be running on a battery backup or if power goes out you could be hosed by enabling the cache. Below is a tutorial explaining the full process to do so.

    http://www.1337admin.org/windows-server/windows-server-2012-r2/dell-h200-raid-controller-speed-hack/

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