Poor performance with NFS

[Claude Fortin]

When I perform a backup with omniback on a nfs
mount point, the performance decrease. I'm able
to backup 4gigs/hour. When I backup a 200 gigs is very very long.

NFS setting or ???

Thanks.

[G. Vrijhoeven]

Hi,

You might be bettor of backing up the nfs mount on the export machine. Its faster and more reliable.

Gideon

[Claude Fortin]

My export machine is not a unix box, is a network storage.

[G. Vrijhoeven]

Hi,

OK its an NAS box. They should be supporting the NDMP protocol (backup protocol). Check if your backup application supports this (Legato does)

Gideon

[Claude Fortin]

The problem is also seen when transfering files to and from the device.
First test: A windows machine can get 24gb/h
from the unit.
Second test: Full trace (sniffer)of transfer between HP box and device. Transfer procedes at 24gb/h (sub 1s intervals)every so often hp-ux waits 1.8-2s before issuing next request even though all request are completed.

These 2s hesitations happen often enough to slow the process down to 4gb/h over an 8-10 second interval.

Why is hp-ux stalling?

Thanks

[Wodisch]

Hello Claude,

perhaps too simple questions, but anyway:
- have you increased the amount of NFS-client processes in "/etc/rc.config.d/nfsconf" on the Omniback-machine?
- have you checked for all those NFS-options, like packet-sizes (read and write), retry-rates, timeouts, and such for your NFS-mount on the Omniback-machine?
Have you checked for your locla buffer-cache? Too smal is bad bad too big is bad, too... (somewhere about 100-300MB seems the best size for most stations)

Just my ???0.02,
Wodisc

[Bill Hassell]

A couple of other notes on performance: NFS is networking and Omniback is crucially dependent on hostname/IPaddress information. If you have a DNS server, all Omniback cell servers should implement /etc/hosts for hostnames/IPaddr that will be part of a backup. Change nsswitch.conf to look at files, then dns. This is a reliability feature as well as performance. If a DNS goes offline, EVERY file will requrie a 20-30 second timeout before it can be backed up.

Also, look at nfs stats. You may need to increase the number of client (cell server) daemons to make sure they can keep up with the NAS box.