topic Re: Backup Process Using 100% CPU in Operating System - HP-UX

Backup Process Using 100% CPU

Jim Sobiesczyk — Fri, 06 Jan 2006 12:48:10 GMT

I'm new to HPs and also for the company I'm working for. But I have a backup script that has the following in it:
-----------------------------------------------
#Always backup root filesystem
#
FS=/
echo "Starting backup of \"$FS\" `/bin/date`." >>$BACKUPLOG
cd $FS
find . -print | \
grep -v '/arc' | \
grep -v '/intra' | \
grep -v '/curly' | \
grep -v '/tempgis' | \
grep -v '/photos' | \
cpio -oBcdmuv > $NOREWIND_TAPE 2>$BACKUPDETAIL
echo "Backup of \"$FS\" completed `/bin/date`." >>$BACKUPLOG

# Run backup loop in subshell, and tee output to the backup log
(cat $FSYS | while read FS
do
echo "Starting backup of \"$FS\" `/bin/date`."
echo "Starting backup of \"$FS\" `/bin/date`." >>$BACKUPDETAIL
cd $FS
find . -print | cpio -oBcdmuv > $NOREWIND_TAPE 2>>$BACKUPDETAIL
echo "Backup of \"$FS\" completed `/bin/date`."
echo "Backup of \"$FS\" completed `/bin/date`." >>$BACKUPDETAIL
done) >> $BACKUPLOG
---------------------------------------------_

This is an HP9000 running HP-UX 11.00, which was created using Ignite-UX. The system has 1 Processor, 32 bit, 256 MB memory, and 2 swap spaces of 128MB each.

The CPU is running at 100% for the duration of the backups, and I do not see any apparent problems during this timeframe.

Any advice would be greatly appreciated.

Re: Backup Process Using 100% CPU

Bill Hassell — Fri, 06 Jan 2006 13:31:50 GMT

I don't see where your script has defined NOREWIND_TAPE and since the script does not use "set -u" to prevent errors like this, you may want to see if the tape drive is actually running during the backup. CPU at 100% seems a bit high for a simple backup, even for this very small system. Does top report cpio as the user of all the CPU time?

Re: Backup Process Using 100% CPU

Jim Sobiesczyk — Fri, 06 Jan 2006 14:06:40 GMT

Bill Hassell:

Thanks for your reply and I guess I should've given you at least 4 points... Anyhow, Here's the tape Defs I didn't originally include:

NOREWIND_TAPE=/dev/rmt/1mn
REWIND_TAPE=/dev/rmt/1m

And there -s no "set -u" within the script, so I don't know what that provides.

The backup runs between 1900 and 2200 hrs so I have no idea if the tape light's blinking.

I use sar for my daily Performance check, is it possible to run top thru CRON (maybe AT) to monitor during that timeframe?

Re: Backup Process Using 100% CPU

Patrick Wallek — Fri, 06 Jan 2006 14:26:16 GMT

It is entirely possible that you have more than 1 issue here.

First, this is a rather small machine especially RAM-wise. 128 MB is not much for 11.0.

What may be happening is that the backup kicks off and the find commands run. Doing a find can impact a machine since it has to traverse down the mountpoing you are running it on. The find is also piping the output to cpio to write to the drive. What **MIGHT** be happening is that find is using a few resources, and cpio is using a few resources, but with only 128MB ram, you are using up the available resources and causing the system to page out. If that starts happening then you can severely impact a systems performance.

You can run top periodically and have it write its output to a file. Use the '-f filename' option to top. Have a look at 'man top' for more information on the options available to you with top.

You might also consider running a periodic 'swapinfo -tam' to check your swap utilization during the time the backup runs.

Re: Backup Process Using 100% CPU

Jim Sobiesczyk — Fri, 06 Jan 2006 15:52:44 GMT

Patrick Wallek:

Thanks for the feedback. Those were pretty much my suspicions too. There's no other processes running during that timeframe, so I'll just run a 'swapinfo' cronjob during that timeframe. Not sure they'll spring for the memory as it's pretty expensive; They'd be going for a ne server instead.

Re: Backup Process Using 100% CPU

Jim Sobiesczyk — Fri, 06 Jan 2006 15:52:59 GMT

Re: Backup Process Using 100% CPU

Bill Hassell — Fri, 06 Jan 2006 19:10:17 GMT

set -u should be stanbdard for all scripts to prevent errors, sometimes catastrophic. The shell assumes that all variables are undefined and are given a null value. So if you created a script to remove all the files and directories in tmp, you might do this:

DIRNAME=tmp
rm -rf /$DIRNAM

(DO NOT TRY THIS ON YOUR SYSTEM)
Oops, there's a slight mistake. $DIRNAM should be $DIRNAME. But the shell doesn't know that and the resultant statement now reads:

rm -rf /

That statement is the end of your system--all files and directories on all disks will be removed with no recovery excepty re-install. Now if the set -u was inserted in the front of the script, the rm statement would not be executed because $DIRNAM is undefined and the script stops.

Re: Backup Process Using 100% CPU

Ted Buis — Tue, 10 Jan 2006 20:42:33 GMT

You have very little RAM, but even more is the minimal swap space. It is hard to believe that you don't have more problems with so little virtual address space.

Re: Backup Process Using 100% CPU

Jim Sobiesczyk — Thu, 23 Feb 2006 12:52:59 GMT

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