[TriLUG] NFS write performance problem

[Jason Tower]

what does hdparm give you on /dev/md0?

the hdparm results for /dev/hdc are a little troubling, there is no reason the 
secondary ide channel should be substantially slower than the primary.  is 
there a cdrom on /dev/hdd?  try running gkrellm with seperate panels for hda 
and hdc, maybe that will give you a hint.

also FWIW, i've had good luck using PCI ide controller cards instead of the 
onboard controllers, especially on systems without ata/66 or ata/100 support.  
they seem to be faster than many onboard ide controllers (better hdparm 
results) and work with large disks (some motherboards choke on disks >32GB).   
CSO sells them for $6 apiece at the moment, i just ordered four more for my 
collection.

jason

On Friday 27 December 2002 14:08, Scott Stancil wrote:
> I am having NFS write performance issues with a backend dedicated NFS
> server (RedHat 8.0, PIII 550, 128MB ram, 100Mbps network).  The client (RH
> 6.1, Kernel 2.2.19SMP with nfs-utils-0.1.9.1-1, dual PIII 550's, 1GB ram,
> 100Mbps network) is mounting the home directory off of the server.
> Integrated Intel EtherExpress 100 ethernet devices on both.
>
> Testing Methods:
> I am using the following to test the network transfers from the client to
> the server.
>  Write:
>  time dd if=/dev/zero of=/mnt/home/testfile bs=x count=y
>
>  Read:
>  time dd if=/mnt/home/testfile of=/dev/null bs=x
>
>
> Results:
> Unmounts between changes to clear caching. Reading and writing a 262MB
> file.
>
> X=8 Y=32768, Write=2:48, Read=0:10, 1.55 MB/second, 24.25MB/second read
>
> X=16 Y=16384, Write=2:48, Read=0:25, 1.55 MB/second write, 10.5 MB/second
>
> read X=32 Y=8291, Write=2:48, Read=0:15, 1.55MB/second write, 17.5
> MB/second read
>
>
> Hard drive settings:
>
> RAID 1 EIDE drives are showing the following with "hdparm -Tt /dev/hda".
>
> /dev/hda:
>  Timing buffer-cache reads:   128 MB in  1.33 seconds = 96.24 MB/sec
>  Timing buffered disk reads:  64 MB in  1.39 seconds = 45.96 MB/sec
>
> /dev/hdc:
>  Timing buffer-cache reads:   128 MB in  1.33 seconds = 96.24 MB/sec
>  Timing buffered disk reads:  64 MB in  2.31 seconds = 27.68 MB/sec
>
> This doesn't suprise me as I suspect that the secondary controller is not
> quite as fast as the primary controller, but still well above the read
> bottleneck.
>
> hdparm <device>:
>
> /dev/hda:
>  multcount    = 16 (on)
>  IO_support   =  0 (default 16-bit)
>  unmaskirq    =  0 (off)
>  using_dma    =  1 (on)
>  keepsettings =  0 (off)
>  readonly     =  0 (off)
>  readahead    =  8 (on)
>  geometry     = 4865/255/63, sectors = 78165360, start = 0
>
> /dev/hdc:
>  multcount    = 16 (on)
>  IO_support   =  0 (default 16-bit)
>  unmaskirq    =  0 (off)
>  using_dma    =  1 (on)
>  keepsettings =  0 (off)
>  readonly     =  0 (off)
>  readahead    =  8 (on)
>  geometry     = 77545/16/63, sectors = 78165360, start = 0
>
>
> Although this is a test server and I can mess with it as much as I want, I
> would prefer not to perform a reinstall if at all possible. :)
>
> 1.  I have examples of testing reads from the disk performance, but what
> might I use to test writes, especially to a RAID 1 slice/partition?
> 2.  Geometry is "off" in /dev/hdc or is it?  It has worked without
> complaint for about a month now, but they are identical disks and the
> geometry is way off.  Could the difference in controllers cause this?
> 3.  Anyone have any ideas on how to improve the pitiful write performance?
> Or perhaps how to benchmark/troubleshoot my performance a little better?