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Old 09-22-2010, 03:18 PM   #1
tilsleyj
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Amt of Memory truly being used.


All,

Fairly new to Linux, using Red Hat ES 5.5 with 16GB of memory. Looking at migrating the server to a VMWare VM, but I need to figure out how much of the 16GB I am actually using. What are some ways to tell the true amount that I need. I know that Red Hat allocates most of the memory just so it is ready to be used, so that throws me off a bit.

Thanks,

Jerry
 
Old 09-22-2010, 03:22 PM   #2
John VV
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is that 16 gig of ram ? or 16 gig of hard disk space
if ram you will need the rhel 64 bit OS otherwise only 3.3 gig wil be usable ( 3.99999 gig using the PAE kernel ) with the rhel 5 32 bit OS
 
Old 09-22-2010, 04:04 PM   #3
Tinkster
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Quote:
Originally Posted by John VV View Post
is that 16 gig of ram ? or 16 gig of hard disk space
if ram you will need the rhel 64 bit OS otherwise only 3.3 gig wil be usable ( 3.99999 gig using the PAE kernel ) with the rhel 5 32 bit OS
Ummm ... actually you can (albeit more slowly and
cumbersome) address up to 64GB with PAE on a 32-bit
Linux - not 4GB.


To the OP:

Code:
$ free
             total       used       free     shared    buffers     cached
Mem:       3940016    3395464     544552          0      21700    1210168
-/+ buffers/cache:    2163596    1776420
Swap:      2104472     300792    1803680
Red - Green gives you the ram actually allotted to running
processes, rather than cache and buffers. Be generous, though,
swapping will penalise performance.



Cheers,
Tink
 
Old 09-22-2010, 04:15 PM   #4
TobiSGD
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To get the true amount of RAM currently being used I would recommend the ps_mem.py script. http://www.pixelbeat.org/scripts/ps_mem.py
 
Old 09-22-2010, 04:20 PM   #5
MrCode
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This is actually a decent page that explains (albeit in layman's terms) how memory is managed in Linux. Just ignore the "panicky" look of it; it really does contain useful information.

Last edited by MrCode; 09-22-2010 at 04:21 PM.
 
Old 09-29-2010, 03:07 PM   #6
tilsleyj
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Thanks all! MrCode, that page was great! It allowed me to verify my memory usage. Currently the server does have 16GB of memory, but I am wanting to move it to virtual and needed to verify how much is truly used. I am now recording the amount used every 3 minutes for the next week or so to see how it looks. Currently the server is using a stunning 1.04GB! What a wonderful waste of a big server!!

Again, thanks everyone for the help!
 
Old 09-29-2010, 03:56 PM   #7
Tinkster
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Quote:
Originally Posted by tilsleyj View Post
Currently the server is using a stunning 1.04GB! What a wonderful waste of a big server!!

Again, thanks everyone for the help!
Don't think of it as waste; there's a good chance that
the machine works snappily because lots of data is held
in the "wasted" space.


Cheers,
Tink
 
  


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