[ILUG] NFS throughput drops with SCSI activity
airlied at csn.ul.ie
Thu Apr 26 13:35:03 IST 2001
I'd go with the swap network-card suggest also ... eepro Intel card or
later 3c900 series (with latest driver).
On Thu, 26 Apr 2001, Kenn Humborg wrote:
> Machine: HP Vectra PPro 200MHz
> dual-proc board with 1 CPU
> Kernel: 2.2.18 uniprocessor
> Ethernet: Netgear FA311 100BaseT
> Netgear-supplied driver
> SCSI: Adaptec AIC-7880U on-board
> aic7xxx driver
> DISK: Seagate ST32171N
> I'm setting this machine up to pull disk images from an
> NFS server and write them to the disk. There is no other
> local disk storage available, so the images are pulled
> across NFS piped to gzip and dumped to the disk.
> Reading the image and dumping it to /dev/null gives me
> 2MB/s average across the network. (In fact, it peaks
> around 4.5MB/s, but is very bursty - don't know why, but
> don't really care, since the CPU can only decompress at
> about 2MB/s average anyway.)
> dd-ing from /dev/zero to the SCSI disk gives about 6MB/s,
> which is respectable enough. Given an approx compression
> ratio of 3:1 (as seen in practice) this matches nicely with
> the network and CPU throughput.
> However, while writing to the disk, NFS throughput drops
> to about 0.5MB/s and I get "server timed out" & "server OK"
> messages a lot. Sometimes NFS practically halts. (Note
> that this happens even when the NFS and disk commands are
> not in the same pipeline, so it's that the pipes are getting
> I've tried using irqtune to make the NIC's interrupt higher
> priority than the SCSI adapter's, but it makes no difference.
> What could be causing the slow-down and how might I fix it?
David Airlie, Software Engineer
http://www.skynet.ie/~airlied / airlied at skynet.ie
pam_smb / Linux DecStation / Linux VAX / ILUG person
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