NFS Performance Tuning for HP-UX 11.0 and 11i Systems

nfs performance tuning for hp-ux 11.0 and 11i systems page 91

Notes:

Page 91July 22, 2002

How is 11i PV3 different from 11.0?

nfs pv2

vs.

nfs pv3

Difference between 11.0 and 11i

Ø The largest file size supported by an 11.0 NFS PV3 client is 1TB.

11i PV3 clients can access files as large as 2TB.

Ø When HP-UX 11.0 released, the largest read and write buffer size

available for an NFS PV3 mountpoint was 8KB. Support for 32KB

read and write requests were added in March 2000. 11i

ships with support for 32KB read and write requests.

Ø Even though HP-UX 11.0 now supports 32KB read and write buffer

sizes, the default remains 8KB for PV3 mounts. The default

read and write buffer sizes on 11i is 32KB for PV3 mount points.

The differences between HP-UX 11.0 and 11i that allow an 11i client to access a

larger file are not due to variations in the NFS implementations, but rather

differences in some of the supporting protocols that NFS is dependent on.

For example, the NLM (Network Lock Manager) protocol shares key kernel variable

definitions with the underlying local VxFS filesystem. NLM is therefore subject to

the same file size limitations as VxFS. In other words, an HP-UX 11.0 NFS PV3

client may be able to WRITE a file larger than 1TB (assuming it is writing this file to

an NFS PV3 server that supports files larger than 1TB), but the client would not be

able to set a LOCK on the file at an offset greater than 1TB. Again, this is not a

limitation of NFS itself, but of NLM.

Since NFS relies on NLM for file locking semantics, this NLM limitation does

impose a limit on the maximum file sizes supported by HP-UX NFS clients.