[hobbit] Memory check

[Rolf Schrittenlocher]

Hi,

>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 cached
>Mem:        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.
>
>
>
>  
>
We are working with Solaris 9 and for them unfortunately there is no 
ACTUAL MEMory presented. But PHYSical MEMory is always high on some 
machines runing a database in warm standby for the same reasons as 
Henrik explained. In other words: The way it is this test is useless for 
us. I'd prefer other columns of vmstat checked as io, etc. Did anyone 
work in this direction or where have I to dig in trying these changes?

regards
Rolf

>-- 
>Mit freundlichen Gruessen
>Rolf Schrittenlocher
>
>HRZ/BDV, Senckenberganlage 31, 60054 Frankfurt 
>Tel: (49) 69 - 798 28908   Fax: (49) 69 798 2881
>LBS: lbs-f at mlist.uni-frankfurt.de
>Persoenlich: schritte at rz.uni-frankfurt.de
>
>  
>