i have a computer running slackware 9.1 with kernel 2.6.1 that i've set to backup daily via a simple tar backup script in cron.daily. the data being backed up probably amounts to several hundred MB per day for the incremental backup and >2GB once a week/month for a full backup. it is backing up to a samba mounted drive (100mbps connection).

here's the weird part... every morning after it has backed up, all of the computer's RAM is used up and it has to be rebooted to free the RAM. this computer has a gig of RAM.

when i run top and sort by memory usage, the memory doesn't add up to what's being used. furthermore, the memory isn't freed when it's needed. i have an image analysis package that requires >512MB RAM and there is a marked decrease in performance when it's run after a daily backup.

backups to local drives give me no problem. am i missing something fundamental here?

thanks in advance.

Sounds like a kernel bug.
The 2.6 release is new, some problems are to be expected.
2.6.2 is out now.
You might be better with a 2.4 kernel.

What does
$free
show? Linux has a tendency to cache stuff in RAM in case it needs to be used again. I run a server with 1.5 gB of RAM and when I am busy, usage of RAM rises to 1.5gB but most is cached stuff. It does not affect performance at all. In a multiuser system this is a great benefit. The first user loads OpenOffice from the HD and the next gets it from RAM.
You likely do not see much degradation in service until swap rises a bit. I suspect Linux has just cached everything you have backed up.
Try
$vmstat
the si and so columns are swaps in and out in kB/s.