I'm not sure on the details, but I believe the Linux kernel loads up a large percentage of available memory with disk buffers as files are read. Those buffers don't really count against any process and will be evicted as soon as an actual process asks for real memory. The idea is that it speeds up disk access for those files that are in memory, and doesn't cost much (in machine time) to keep them around until the space is needed for something else.
Memory usage spikes during a backup because it's reading *all* the files on disk...
Ralph Mitchell
On 2/7/06, David Gilmore <david at stenhouseconsulting.com> wrote:
My hobbit server (Fedora FC4) has 1.25 gig of memory installed. When the server is backed, up using Retrospect client, REAL memory usage spikes from 34% to 97% and stays at that level until a reboot. When I check the system performance, using the built in system monitor, user memory is at 18.9%. Dell Open Manage is using the most memory at 3% with a few additional processes between 1% and 2%. Everything else is well under 1%. What exactly is hobbit reporting on when it says that Physical/Real memory is at 97%, Actual memory is at 17%, and Swap is at 0%?
Thanks,
David Gilmore Consultant Stenhouse Consulting, LLC. 4 Traverse St Providence, RI 02906 401.453.6900 401.454.7581 (fax)