Ok I understand the concept. However, I don't want to continue to receive Alerts because Linux is doing exactly what it is designed to do. Does anyone have a script that can clear the buffers and stop hobbit from paging me? Can I modify the script to only alert when REAL memory is at 100% or higher? Or do I have to reboot my server ever morning to resolve this alert? I currently have the alerts disabled, but I am concerned that I could miss a critical error
Dave
-----Original Message----- From: hobbit-return-5584-david=stenhouseconsulting.com at hswn.dk [mailto:hobbit-return-5584-david=stenhouseconsulting.com at hswn. dk] On Behalf Of Henrik Stoerner Sent: Wednesday, February 08, 2006 1:45 AM To: hobbit at hswn.dk Subject: Re: [hobbit] Memory check
On Tue, Feb 07, 2006 at 07:41:23PM -0500, David Gilmore 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%?
Hobbit reports the output from the "free" command. It probably looks somewhat like this after you've run a backup:
total used free shared buffers cachedMem: 646432 642172 4260 0 167676 136068 -/+ buffers/cache: 338428 308004 Swap: 511992 4 511988
The "Mem" line here tells you that there is 640 MB RAM installed, and all except 4 MB is being "used". However, a lot of that is used for "buffers" and "cache", which is the Linux kernel's dynamically resized disk cache; if an application needs more RAM that is "free", the disk cache/buffers are discarded and the memory made available to the application.
So that's why the "-/+ buffers/cache" line is interesting: This shows the used/free memory count if the buffers/cached is counted as "free" memory. Hobbit report this as the "actual" memory count.
So a Linux system will practically always have a REAL memory usage close to 100% (Linus Torvalds once said that "unused RAM is *wasted* RAM, and there's no reason to spend lots of money on something that isn't used" - quoting from memory). The ACTUAL memory usage (should) be a lot less, and is what you'll want to keep an eye on.
Regards, Henrik
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