Date: Thu, 26 Feb 2004 17:46:31 -0500 From: Charles Swiger <cswiger@mac.com> To: Michael Conlen <meconlen@obfuscated.net> Cc: freebsd-questions@freebsd.org Subject: Re: NFS server usage Message-ID: <9F44162A-68AD-11D8-870A-003065ABFD92@mac.com> In-Reply-To: <CE6F38ED-68A6-11D8-A5DD-00039367611E@obfuscated.net> References: <478667A6-6892-11D8-A5DD-00039367611E@obfuscated.net> <5FCEDFA8-68A3-11D8-870A-003065ABFD92@mac.com> <CE6F38ED-68A6-11D8-A5DD-00039367611E@obfuscated.net>
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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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