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

nfs performance tuning for hp-ux 11.0 and 11i systems page 36

Notes:

Page 36July 22, 2002

Why would an NFS client perform

better with NO biods running?

• If biods are running then the number of biods roughly defines the

maximum number of simultaneous outstanding requests possible.

• If NO biods are used, the number of processes simultaneously

reading from or writing to the NFS-mounted filesystems roughly

defines the maximum number of outstanding requests possible.

• Does your NFS client have more reading/writing processes than

biods? If so, you might get better NFS performance with no biods.

biod

GOAL: To achieve optimal throughput, maximize the number of

simultaneous requests “in flight” to the NFS servers

Since any process on the NFS client that tries to read from or write to an NFS

mount point will block if biod processes are running (to allow the biod processes to

perform the I/O on their behalf), it stands to reason that the maximum number of

simultaneous I/O operations an NFS client with biods running can perform is equal

to or near the number of running biods. In other words, if 4 biods are running on

the client then in most cases only 4 NFS read or write calls can occur at any one

time.

If an NFS client has a number of processes simultaneously trying to read from

and/or write to NFS servers, and this number of processes is greater than the

number of running biods, it is possible that the client would experience better NFS

performance if no biods were running. For example, if there are 4 biods running

on the client but there are 100 processes trying to simultaneously read and write to

the NFS servers, these 100 processes will block and wait for the 4 biods to service

these requests on their behalf. If, however, there were no biod daemons running,

each of the 100 processes would send their NFS requests to the respective servers

on their own behalf, potentially resulting in higher throughput.