How to increase RAM memory capacity in RHEL5 ?

[Yaboto]

Hi,

My RHEL5 server has been originally installed with 24GB of RAM memory modules.
I have recently upgraded the RAM to 32GB.
At the server level I could see the new upgraded capacity of 32GB been detected, but not at the RHEL5 OS level. The RHEL5 OS is still seing only the original 24GB.

What commands in RHEL5 are used to determine and check the amount of memory ?

How would I effect the physicall upgrade into the RHEL5 OS ?

Thanks

[Modris Bremze]

Is that RHEL 64bit?

Check memory with either:
cat /proc/meminfo | grep -i memtotal
free -m

[dirk dierickx]

very confusing, you're saying that the OS only sees 24GB ram, and then ask how to check what the commands are to check the amount of RAM.

what command did you use to conclude RH5 still only sees 24GB of ram?

[SoorajCleris]

I have the same query mention above by Drick!!!

[SoorajCleris]

Sorry for the typo drik

Regards,
Sooraj

[Dennis Handly]

>Sooraj: Sorry for the typo drik

(Perhaps you should use cut&paste. ;-)

[SoorajCleris]

He he he :)

[Arockiasamy]

Mr, Yaboto,

At first, Check the RAM installed properly or not.
Check the RAM speed.
Check the RAM slots.
Check in BIOS whether its showing 32GB or not.
Then check with cat /proc/meminfo & free.

If it is not showing in BIOS, that is hardware problem. Then check the RAM with other machine & confirm it.

It maybe the hardware problem.

[Yaboto]

Please the 32GB is showing in the BIOS, but only 24GB is showing in the RHEL5 OS.

After physically upgrading a RAM memory, do we need to rebuild the kernel or setting some memory parameters in RHEL5 OS before the RHEL5 OS sees the new upgraded size ?

If yes, how to do it ?

[Viktor Balogh]

Hi,

>After physically upgrading a RAM memory, do we need to rebuild the kernel or setting some memory parameters in RHEL5 OS before the RHEL5 OS sees the new upgraded size ?

I am not aware of any limit around 24Gig. A 4 Gigabyte limit is there, above that you should use a PAE-enabled kernel, which supports RAM up to 64GB. 24GB shouldn't be a logical limit if we think it over with a base-2 number system, but fixme.

Regards,
Viktor

[TwoProc]

I've never heard of such a limit at 24Gb, if you're seeing 24Gb, then you must be running either 64bit OS, or 32bit PAE OS, both of which can address more then 24Gb.

[Steven E. Protter]

Shalom,

There is no 24 GB limit in RHEL5. If you were using the 32 bit OS, the system would report only 4 GB of ram.

This system is running 64 bit OS as far as I can tell and is not reporting 8 GB of its memory.

You may have exceeded the servers hardware capacity or have bad memory in the system. You could also have hardware that requires memory go into paired slots and not be complying with hardware guidelines.

uname -a
# please post

SEP

[TwoProc]

I'm thinking that maybe it's time for a firmware update for that system. Motherboard, bios, etc. The only thing I can come up with is that there is a bug in the firmware layer.

One more thing to try, just for clarity - download one of the iso's for another Linux " live" variant: 64 bit Ubuntu, etc. I'm talking about one that will let you try the OS directly from the CD (or USB memory stick) without doing an install of OS. See what those report to you. If you try several 64bit OSs ( maybe RH, Ubuntu, Suse, Knoppix, Fedora) and they all come up with only 24Gb even though you can "see" 32Gb from the BIOS setup, then I'm betting firmware is an issue.

If other OS's see your ram fine, but not your installed one, it's time to look for a patch, open a call with Redhat support, or both.

[Viktor Balogh]

Hi Yaboto,

Are the newly installed DIMMs from the same vendor? And of the same size? Even though the BIOS sees the DIMMs and shows 32GBytes it might be that the newly added ones are not fully compatible with the old ones, because of interleaving. Check the manual for your hardware and look for the maximum supported RAM.

Regards,
Viktor

[Gerardo Arceri]

Also the "dmidecode" command can be useful to see if the system is seeing the additional memory, if you don't see it there then there is probably a problem with it.