Find the answer to your Linux question:
Page 1 of 2 1 2 LastLast
Results 1 to 10 of 12
Hi, I have two HP servers which have CentOS 5.7 installed. One with 48GB RAM and the other one with 96GB RAM. When the machines are being booted, the memory ...
Enjoy an ad free experience by logging in. Not a member yet? Register.
  1. #1
    Just Joined!
    Join Date
    Jan 2011
    Posts
    14

    CentOS version 5.7 the memory not being recognized


    Hi,
    I have two HP servers which have CentOS 5.7 installed.
    One with 48GB RAM and the other one with 96GB RAM.
    When the machines are being booted, the memory sizes are showing correctly. But after booted, the memory sizes show 32GB for both servers (using cat /proc/meminfo, command "top" ,or System monitor).
    Followed the suggestion found from internet, I added mem=xxM (replaced xx with the corresponding RAM size) to /boot/grub/grub.conf and rebooted the servers, but I still get RAM size as 32GB. I cannot figure out what is going wrong.
    Any help will be greatly appreciated...

    -- Annie

  2. #2
    Linux Guru Rubberman's Avatar
    Join Date
    Apr 2009
    Location
    I can be found either 40 miles west of Chicago, in Chicago, or in a galaxy far, far away.
    Posts
    11,508
    What kernel are you running? Post the output of uname -r here.
    Sometimes, real fast is almost as good as real time.
    Just remember, Semper Gumbi - always be flexible!

  3. #3
    Just Joined!
    Join Date
    Jan 2011
    Posts
    14
    Thanks for the reply. the output of uname -r is:
    2.6.18-274.3.1.el5xen

  4. #4
    Linux Guru Rubberman's Avatar
    Join Date
    Apr 2009
    Location
    I can be found either 40 miles west of Chicago, in Chicago, or in a galaxy far, far away.
    Posts
    11,508
    So this is probably a 32-bit PAE-enabled system. It isn't native 64-bit for sure I think. If so, then I believe that PAE (Physical Address Extensions) only gives you 32GB of real memory space. Have you tried the x86_64 system? That should handle the 48GB of physical ram that you have.
    Sometimes, real fast is almost as good as real time.
    Just remember, Semper Gumbi - always be flexible!

  5. #5
    Just Joined!
    Join Date
    Jan 2011
    Posts
    14
    My servers are HP ProLiant DL 165 G7 (64bit server) and both have CentOS 5.7 64bit installed. the output for uname -a is:

    Linux headnode 2.6.18-274.3.1.el5xen #1 SMP Tue Sep 6 20:57:11 EDT 2011 x86_64 x86_64 x86_64 GNU/Linux

    thanks again for the help

  6. #6
    Linux Guru Rubberman's Avatar
    Join Date
    Apr 2009
    Location
    I can be found either 40 miles west of Chicago, in Chicago, or in a galaxy far, far away.
    Posts
    11,508
    Ok. It may be that the xen extensions are causing this. Do you need Xen in the kernel? Are you using Xen virtual machines?
    Sometimes, real fast is almost as good as real time.
    Just remember, Semper Gumbi - always be flexible!

  7. #7
    Just Joined!
    Join Date
    Jan 2011
    Posts
    14
    I am not very familiar with linux system and this is my first time to hear about Xen virtual machines (just did a bit browsing on what was Xen from the internet )
    These two servers are configured as cluster system with PBS TOUQUE and some third party software installed. I don't think I am using Xen virtual machines.
    But I like to know how to check it just in case. Really appreciate all of your helps and you have a nice weekend.

  8. #8
    Linux Guru Rubberman's Avatar
    Join Date
    Apr 2009
    Location
    I can be found either 40 miles west of Chicago, in Chicago, or in a galaxy far, far away.
    Posts
    11,508
    You can install the regular x86_64 kernel and remove the xen kernels easily enough using yum. CentOS 5.x installs the xen kernels by default. I had a similar problem when I started using it several years ago, and had to remove the xen kernel because I could not install the proprietary nVidia video driver with it installed. In any case, you can first use yum to install the non-zen kernel and select that one to boot from the grub menu.
    Sometimes, real fast is almost as good as real time.
    Just remember, Semper Gumbi - always be flexible!

  9. #9
    Just Joined!
    Join Date
    Jan 2011
    Posts
    14
    Thanks for all your replies and I will give it a try next Monday.

  10. #10
    Just Joined!
    Join Date
    Jan 2011
    Posts
    14
    The problem has been solved based on your suggestion and now all the RAM can be recognized. I modifed the file /boot/grub/grub.conf to change the
    booting order, by default it was booted to Xen mode. I have one more question like to get advice from you, I will redo the servers to have CentOS 6.0 installed,
    how can I have regular x86-64 kernerl installed at the first place other than changing it later?

    thank you for all your helps and you are indeed a Linux Guru !

Page 1 of 2 1 2 LastLast

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •