Hi All:
I have an HP DL380G5 server which I am loading CentOS 6.2 on and it does not appear to recognize all of the RAM installed on the server. The BIOS is reporting 26GB however top is reporting:
Mem: 15720140k total, 418988k used, 15301152k free, 30256k buffers Swap: 17956856k total, 0k used, 17956856k free, 135536k cached
and free is reporting:
total used free shared buffers cached Mem: 15720140 418848 15301292 0 30256 135536 -/+ buffers/cache: 253056 15467084 Swap: 17956856 0 17956856
I have tried adding the mem= parameter to the /boot/grub/grub.conf file as in:
title CentOS (2.6.32-220.17.1.el6.i686) root (hd0,0) kernel /vmlinuz-2.6.32-220.17.1.el6.i686 ro [SNIP] initrd /initramfs-2.6.32-220.17.1.el6.i686.img mem=26624M
but this has not appeared to work.
Any suggestions would be gratefully appreciated.
TIA
Regards, Hugh
on 6/19/2012 3:37 PM Hugh E Cruickshank spake the following:
Hi All:
I have an HP DL380G5 server which I am loading CentOS 6.2 on and it does not appear to recognize all of the RAM installed on the server. The BIOS is reporting 26GB however top is reporting:
Mem: 15720140k total, 418988k used, 15301152k free, 30256k buffers Swap: 17956856k total, 0k used, 17956856k free, 135536k cached
and free is reporting:
total used free shared buffers cachedMem: 15720140 418848 15301292 0 30256 135536 -/+ buffers/cache: 253056 15467084 Swap: 17956856 0 17956856
I have tried adding the mem= parameter to the /boot/grub/grub.conf file as in:
title CentOS (2.6.32-220.17.1.el6.i686) root (hd0,0) kernel /vmlinuz-2.6.32-220.17.1.el6.i686 ro [SNIP] initrd /initramfs-2.6.32-220.17.1.el6.i686.img mem=26624M
but this has not appeared to work.
Any suggestions would be gratefully appreciated.
TIA
Regards, Hugh
It looks like you installed 32 bit OS... I don't think it sees over 16 gigs...
From: Scott Silva Sent: June 19, 2012 15:51
It looks like you installed 32 bit OS... I don't think it sees over 16 gigs...
Yes it is 32-bit but if there is a 16GB limit on memory then I am going to need to revert to CentOS 5.
Regards, Hugh
On Tuesday 19 June 2012, "Hugh E Cruickshank" hugh@forsoft.com wrote:
Yes it is 32-bit but if there is a 16GB limit on memory then I am going to need to revert to CentOS 5.
Same limit in CentOS 5.
Is there a reason you don't want to use x86_64?
From: Joseph L. Casale Sent: June 19, 2012 15:52
title CentOS (2.6.32-220.17.1.el6.i686) root (hd0,0) kernel /vmlinuz-2.6.32-220.17.1.el6.i686 ro [SNIP] initrd /initramfs-2.6.32-220.17.1.el6.i686.img mem=26624M
Do i read that right? 26g of ram and you're using a non PAE x86 kernel?
It was my understanding that PAE is now built into the standard kernel but I will check on this further.
Regards, Hugh
On 06/19/12 4:13 PM, Hugh E Cruickshank wrote:
From: Joseph L. Casale Sent: June 19, 2012 15:52
title CentOS (2.6.32-220.17.1.el6.i686) root (hd0,0) kernel /vmlinuz-2.6.32-220.17.1.el6.i686 ro [SNIP] initrd /initramfs-2.6.32-220.17.1.el6.i686.img mem=26624M
Do i read that right? 26g of ram and you're using a non PAE x86 kernel?
It was my understanding that PAE is now built into the standard kernel but I will check on this further.
If I recall correctly, PAE is limited to 16GB because the page tables are obscenely huge for more than that, and use over a gigabyte of the 32bit kernel space
On Tuesday 19 June 2012, "Hugh E Cruickshank" hugh@forsoft.com wrote:
I have an HP DL380G5 server which I am loading CentOS 6.2 on and it does not appear to recognize all of the RAM installed on the server. The BIOS is reporting 26GB however top is reporting:
Mem: 15720140k total, 418988k used, 15301152k free, 30256k buffers Swap: 17956856k total, 0k used, 17956856k free, 135536k cached
title CentOS (2.6.32-220.17.1.el6.i686)
I can't find the limit for CentOS 6, but CentOS 5 x86 was limited to 16 Gb of RAM: https://www.centos.org/product.html . You should use x86_64.
From: Yves Bellefeuille Sent: June 19, 2012 15:55
I can't find the limit for CentOS 6, but CentOS 5 x86 was limited to 16 Gb of RAM: https://www.centos.org/product.html . You should use x86_64.
If that is the case then both CentOS 5 and 6 are not viable for us. I will have to go for RHEL5 (or possibly 6) which does support the memory in 32-bit mode.
The reason for the restriction to 32-bit is because of other software that we must run that does not work correctly on a 64-bit OS.
Regards, Hugh
on 6/19/2012 4:22 PM Hugh E Cruickshank spake the following:
From: Yves Bellefeuille Sent: June 19, 2012 15:55
I can't find the limit for CentOS 6, but CentOS 5 x86 was limited to 16 Gb of RAM: https://www.centos.org/product.html . You should use x86_64.
If that is the case then both CentOS 5 and 6 are not viable for us. I will have to go for RHEL5 (or possibly 6) which does support the memory in 32-bit mode.
The reason for the restriction to 32-bit is because of other software that we must run that does not work correctly on a 64-bit OS.
Regards, Hugh
You can always virtualize...
On 06/19/12 4:22 PM, Hugh E Cruickshank wrote:
The reason for the restriction to 32-bit is because of other software that we must run that does not work correctly on a 64-bit OS.
fix that other software. or run in 16GB. there's no excuse in 2012 for not supporting 64bit, even my budget laptop has 8GB of memory and a 64bit OS.
as an example of the problems see this message, http://www.redhat.com/archives/rhelv5-list/2008-September/msg00194.html and its various followups...
PAE was a kludge to let 32 bit OS's, normally limited to 4GB max memory address more. the kludge breaks things above 16GB in spite of the theoretical 64GB limit enforced by the hardware.
also see this https://www.redhat.com/resourcelibrary/articles/articles-red-hat-enterprise-...
EL *4* supported a nasty 'hugemem' kernel that could get you past 16GB but only at great overhead. this caused MANY problems and was discontinued in EL5 and 6 32bit systems, where 64bit is the correct choice for all modern servers.
On Tuesday 19 June 2012, "Hugh E Cruickshank" hugh@forsoft.com wrote:
If that is the case then both CentOS 5 and 6 are not viable for us. I will have to go for RHEL5 (or possibly 6) which does support the memory in 32-bit mode.
The limit's the same with RHEL 5 and 6. CentOS is "bug-for-bug compatible" with RHEL.
The reason for the restriction to 32-bit is because of other software that we must run that does not work correctly on a 64-bit OS.
Your 32-bit applications will be restricted to 4 Gb of memory each anyway. If you must use x86, memory over 16 Gb is pretty much wasted, unless you install x86_64 and virtualize x86 as necessary.
On 06/19/12 6:31 PM, Yves Bellefeuille wrote:
Your 32-bit applications will be restricted to 4 Gb of memory each anyway.
sctually, they only get 2 or 3gb of that for user space, the other 1 or 2gb of the 32bit space is used by the kernel which is in every process address space. I believe with PAE, you actually get LESS per process address space
Hi All:
Thanks for all the responses and suggestions. I have been doing some more research and I believe that it may be possible to go 64-bit. I am going to leave this for now and have another look at it in the morning when I am, hopefully, awake before I make the final decision.
Good night.
Regards, Hugh
On Jun 20, 2012, at 2:18 AM, "Hugh E Cruickshank" hugh@forsoft.com wrote:
Thanks for all the responses and suggestions. I have been doing some more research and I believe that it may be possible to go 64-bit. I am going to leave this for now and have another look at it in the morning when I am, hopefully, awake before I make the final decision.
It is definitely the wise choice given the memory requirements.
I have yet to find a 32-bit app that won't run on x86_64, all that is needed is the 32-bit libraries.
Even Microsoft is producing 64-bit only server OS now.
-Ross
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Hugh E Cruickshank -
John R Pierce -
Joseph L. Casale -
Ross Walker -
Scott Silva -
Yves Bellefeuille