Re: NFS server usage

From: Charles Swiger (cswiger_at_mac.com)
Date: 02/26/04

  • Next message: Scott W: "Re: NFS server usage" 
    Date: Thu, 26 Feb 2004 17:46:31 -0500
To: Michael Conlen <meconlen@obfuscated.net>

    On Feb 26, 2004, at 4:57 PM, Michael Conlen wrote:
    > [ ... ]
    > The production system will use dual channel U320 RAID controllers with
    > 12 disks per channel, so disk shouldn't be an issue, and it will
    > connect with GigE, so network is plenty fine, now I'm on to CPU.

    Sounds like you've gotten nice hardware. Four or so years ago, I built
    out a roughly comparible fileserver [modulo the progess in technology
    since then] on a Sun E450, which housed 10 SCA-form-factor disks over 5
    UW SCSI channels (using 64-bit PCI and backplane, though), and could
    have held a total of 20 disks if I'd filled it. I mention this
    because...

    > Low volume tests with live data indicate low CPU usage however when I
    > best fit the graph it's dificult to tell how linear (or non linear)
    > the data is. [ ... ] Does that kind of curve look accurate to you
    > (anyone)?

    ...even under stress testing on the faster four-disk RAID-10 volume
    using SEAGATE-ST336752LC drives (15K RPM, 8MB cache), each on a
    seperate channel, with ~35 client machines bashing away, the fileserver
    would bottleneck on disk I/O without more than maybe 10% or 15% CPU
    load, and that was using a 400MHz CPU.

    The notion that an NFS fileserver is going to end up CPU-bound simply
    doesn't match my experience or my expectations. If you have
    single-threaded sequential I/O patterns (like running dd, or maybe a
    database), you'll bottleneck on the interface or maximum disk
    throughput, otherwise even with ~3.5 ms seek times, multi-threaded I/O
    from a buncha clients will require the disk heads to move around so
    much that you bottleneck at a certain number of I/O operations per
    second per disk, rather than a given bandwidth per disk. 

    -- 
-Chuck
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  • Next message: Scott W: "Re: NFS server usage"

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