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HP-UX System Administrator's Guide: Routine Management Tasks: HP-UX 11i Version 3 > Chapter 6 Managing System Performance



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Performance is a notoriously difficult topic on which to provide definite advice; these guidelines should not be taken as formal recommendations from HP, but merely as the closest the authors could come to distilling a consensus from the observations of the experts they consulted.

  • Keep NFS servers and their clients on the same LAN segment or subnet. If this is not practical, and you have control over the network hardware, use switches, rather than hubs, bridges and routers, to connect the workgroup.

  • As far as possible, dedicate a given server to one type of task.

    For example, in our sample network (see HP-UX System Administrator’s Guide: Overview) flserver acts as a file server, sharing directories to the systems, whereas appserver is running applications.

    If the workgroup needed a web server, it would be wise to configure it on a third, high-powered system that was not doing other heavy work.

  • On file servers, use your fastest disks for the shared file systems, and for swap.

    • 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”.

    • Distribute the disks evenly among the system’s I/O controllers.

  • For shared 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 New NFS File System menu on HP SMH. See “Checking NFS Server/Client Block Size” for directions for checking and changing the values.

  • Enable asynchronous writes on shared file systems.

    See “Checking for Asynchronous Writes”.

  • 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 sharing 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” and “Increasing the Number of nfsd Daemons”.

  • 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”; 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.

    In practice, though, a server is dealing with many I/O requests at a time, and intelligence is designed into the drivers to take account of the current head location and direction when deciding on the next seek.

    This means that defragmenting an HFS file system on HP-UX may never be necessary; JFS file systems, however, do need to be defragmented regularly.

    See “Defragmenting an HFS File System” and “To defragment a JFS file system using fsadm ”.

  • Keep shared files and directories as small as possible.

    Large files require more NFS operations than small ones, and large directories take longer to search.

    Encourage your users to weed out large, unnecessary files regularly (see “Finding Large Files”).

  • Monitor server and client performance regularly.

    See “Measuring Performance”.

Resource Hogs

To get an idea of your top CPU hogs, run HP SMH and select Home, Operating System, Process Information. (Or run /usr/bin/top from the command line.)

To compare memory use by the processes currently running, run ps -efl. Look under the SZ column of the resulting display.

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