hkclark at gmail.com
2007-Feb-09 03:33 UTC
[CentOS] CentOS 3 vs. CentOS 4 Memory Utilization
I'm helping some folks who have a CentOS 3 i386 server with 512MB of RAM. The output of 'free' looks like: $ free total used free shared buffers cached Mem: 511428 497956 13472 0 29868 178280 -/+ buffers/cache: 289808 221620 Swap: 2040244 120644 1919600 The box does not even have X installed... it's basically a web application and email server. They would like to upgrade to CentOS 4, but are concerned that it could be considerably more "memory hungry" and lead to memory starvation (they don't want to add more RAM to the box at this time, although that could be an option down the road). I ran some tests under VMWare with fresh installations of CentOS 3 and CentOS 4 (both using a "minimal install", the same as the server in question) and CentOS 4 seemed to only use 10-25MB more memory. However, it's hard to know how this will translate into real-world performance over time and with the application installed. Does anyone have any experience that would suggest how much more memory a non-X server like this might require? If the application(s) on the server stay the same, do you think we would run into issues where memory would be depleted to a level that would cause concern? Many thanks, KC
On Thu, 2007-02-08 at 22:33 -0500, hkclark at gmail.com wrote:> I'm helping some folks who have a CentOS 3 i386 server with 512MB of > RAM. The output of 'free' looks like: > > $ free > total used free shared buffers cached > Mem: 511428 497956 13472 0 29868 178280 > -/+ buffers/cache: 289808 221620 > Swap: 2040244 120644 1919600 > > The box does not even have X installed... it's basically a web > application and email server. They would like to upgrade to CentOS 4, > but are concerned that it could be considerably more "memory hungry" > and lead to memory starvation (they don't want to add more RAM to the > box at this time, although that could be an option down the road). > > I ran some tests under VMWare with fresh installations of CentOS 3 and > CentOS 4 (both using a "minimal install", the same as the server in > question) and CentOS 4 seemed to only use 10-25MB more memory. > However, it's hard to know how this will translate into real-world > performance over time and with the application installed. > > Does anyone have any experience that would suggest how much more > memory a non-X server like this might require? If the application(s) > on the server stay the same, do you think we would run into issues > where memory would be depleted to a level that would cause concern? >It should not be a problem as lots of your memory used is buffers and cache. CentOS-3 is going to be supported for a while yet (EOL is scheduled for Oct 31, 2010), so if it is working perfectly and doing what they want, they may want to keep it though. If they upgrade or don't, the memory should be OK either way . -------------- next part -------------- A non-text attachment was scrubbed... Name: signature.asc Type: application/pgp-signature Size: 189 bytes Desc: This is a digitally signed message part URL: <lists.centos.org/pipermail/centos/attachments/20070208/8d22aabb/attachment.sig>
On Thu, 2007-02-08 at 22:33 -0500, hkclark at gmail.com wrote:> I'm helping some folks who have a CentOS 3 i386 server with 512MB of > RAM. The output of 'free' looks like: > > $ free > total used free shared buffers cached > Mem: 511428 497956 13472 0 29868 178280 > -/+ buffers/cache: 289808 221620 > Swap: 2040244 120644 1919600 > > The box does not even have X installed... it's basically a web > application and email server. They would like to upgrade to CentOS 4, > but are concerned that it could be considerably more "memory hungry" > and lead to memory starvation (they don't want to add more RAM to the > box at this time, although that could be an option down the road). > > I ran some tests under VMWare with fresh installations of CentOS 3 and > CentOS 4 (both using a "minimal install", the same as the server in > question) and CentOS 4 seemed to only use 10-25MB more memory. > However, it's hard to know how this will translate into real-world > performance over time and with the application installed. > > Does anyone have any experience that would suggest how much more > memory a non-X server like this might require? If the application(s) > on the server stay the same, do you think we would run into issues > where memory would be depleted to a level that would cause concern?--- I wouldn't think so, this system actually does have some x-stuff installed. # cat /etc/redhat-release CentOS release 4.4 (Final) # free total used free shared buffers cached Mem: 515604 509760 5844 0 37832 117296 -/+ buffers/cache: 354632 160972 Swap: 1048568 268324 780244 It's running httpd/php5/mysql-4/postfix/amavisd-new/ejabberd/ntp/cupsd/apcupsd (slave) Craig
hkclark at gmail.com
2007-Feb-09 09:16 UTC
[CentOS] CentOS 3 vs. CentOS 4 Memory Utilization
On 2/8/07, Johnny Hughes <mailing-lists at hughesjr.com> wrote:> > It should not be a problem as lots of your memory used is buffers and > cache. > > CentOS-3 is going to be supported for a while yet (EOL is scheduled for > Oct 31, 2010), so if it is working perfectly and doing what they want, > they may want to keep it though. > > If they upgrade or don't, the memory should be OK either way . >Hi Johnny, Good info -- thanks. They have a small app they want to add that requires a newer version of Perl than 5.8.0 that comes with CentOS 3. Rather than getting into a non-RPM version of Perl, we were thinking going to CentOS 4 would be easier and cleaner. In your experience, would you say that my "quick & dirty" measurement of CentOS 4 needing 10-25 MB more memory than CentOS 3 (again, for a non-X box with a minimal install) is accurate (at least in approximate terms)? Or is there something I'm not taking into account -- e.g, some of the libraries and/or other "basic server apps" such as apache with PHP or MySQL will make that number much higher? Although this box is doing OK on memory now, I would hate to kill their possible expansion plans just because we did an upgrade and it sucked up way more memory than we though. Again, thanks for all the great things you and the CentOS team are doing! Regards, KC