AIX 5L Problem Determination - IBM Redbooks

► Slow mounts from AIX Version 4.2.1 or later, clients running NFS Version 3 to
AIX Version 4.1.5 or earlier and other non-AIX servers running NFS
Version 2. NFS Version 3 uses TCP by default, while NFS Version 2 uses
UDP only. This means that the initial client mount request using TCP will fail.
To provide backwards compatibility, the mount is retried using UDP, but this
only occurs after a timeout. To avoid this problem, NFS Version 3 provides
the proto and vers parameters with the mount command. These parameters
are used with the -o option to hard wire the protocol and version for a specific
mount. The following example forces the use of UDP and NFS Version 2 for
the mount request:
# mount -o proto=udp,vers=2,soft,retry=1 platypus:/test /mnt
► Older non-AIX clients can also incur mount problems. If your environment has
such clients, you need to start mountd with the -n option:
# stopsrc -s rpc.mountd
# startsrc -s rpc.mountd -n
► Another mount problem that can occur with older non-AIX clients is when a
user who requests a mount is in more than eight groups. The only
work-around for this is to decrease the number of groups the user is in or
mount using a different user.
8.4.3 Increasing NFS Socket Buffer Size
You may find that the netstat -s command indicates a significant number of
UDP socket buffer overflows. As with ordinary UDP tuning, increase the sb_max
value. You also need to increase the value of nfs_socketsize, which specifies the
size of the NFS socket buffer. The following is an example:
# no -o sb_max=131072
# nfso -o nfs_socketsize=130972
Note: In AIX Version 4, the socket size is set dynamically. Configurations
using the no and nfso commands must be repeated every time the machine is
booted. Add them in the /etc/rc.net or /etc/rc.nfs file immediately before the
nfsd daemons are started and after the biod daemons are started. The
position is crucial.
8.4.4 The biod and nfsd daemons
Starting with AIX 4.2.1, there is a single nfsd daemon and a single biod daemon,
each of which is multi-threaded (multiple kernel threads within the process). Also,
the number of threads is self-tuning in that it creates additional threads as
needed. You can, however, tune the maximum number of nfsd threads by using
Chapter 8. Network problem determination 191