Managing Systems and Workgroups: A Guide for HP-UX System Administrators

Administering a System: Managing Printers, Software, and Performance
Managing System Performance
Chapter 7728
— Distribute the workload evenly across these disks.
For example, if two teams are doing I/O intensive work, put their
files on different disks or volume groups. See “Checking Disk
Load with sar and iostat” on page 729.
— Distribute the disks evenly among the system’s I/O controllers.
• For exported HFS file systems, make sure the NFS read and write
buffer size on the client match the block size on the server.
You can set these values when you import the file system onto the
NFS client; see the Advanced Options pop-up menu on SAM’s
Mounted Remote File Systems screen. See “Checking NFS
Server/Client Block Size” on page 730 for directions for checking and
changing the values.
• Enable asychronous writes on exported file systems.
See “Checking for Asynchronous Writes” on page 731.
• Make sure enough nfsd daemons are running on the servers.
As a rule, the number of nfsds running should be twice the number
of disk spindles available to NFS clients.
For example, if a server is exporting one file system, and it resides on
a volume group comprising three disks, you should probably be
running six nfsds on the server.
For more detail, see “Checking for Socket Overflows with netstat -s”
on page 733 and “Increasing the Number of nfsd Daemons” on
page 734.
• Make sure servers have ample memory.
Efforts to optimize disk performance will be wasted if the server has
insufficient memory.
Monitor server memory frequently (see “Measuring Memory Usage
with vmstat” on page 732; and never prepare a hardware budget that
doesn’t include additional memory!
• Defragment servers’ JFS file systems regularly.
Fragmentation means that files are scattered haphazardly across a
disk or disks, the result of growth over time. Multiple disk-head
movements are needed to read and update such files, theoretically
slowing response time.