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Redhat Enterprise 5.6 memory upgrade not recognized.

Posted on 2013-11-04
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Last Modified: 2016-11-23
I recently upgraded the RAM in a Dell T610 Server from 32GB to 96GB and when I run a freemem or /cat/meminfo is still shows the original RAM amount. I already:
1. installed all Redhat system and kernel updates.
2. Updated the Grub.conf file to reflect the new memory size.
3. Applied all firmware and bios updates.
4. The BIOS does recognize and passes the memory test.
5. The memory type is Dell original RAM and compatible.
6. Redhat 5.6 supposed to recognize upto 1TB.

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Question by:nickthecomputerguy
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Expert Comment

by:omarfarid
ID: 39623459
Have you done the steps in the link below and specified memory size in MB?

https://access.redhat.com/site/documentation/en-US/Red_Hat_Enterprise_Linux/5/html/Installation_Guide/s2-trouble-ram.html

What is your processor ? Link below show supported processors and memory RAM sizes

http://ae.redhat.com/resourcelibrary/articles/articles-red-hat-enterprise-linux-6-technology-capabilities-and-limits
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Assisted Solution

by:Daniel Helgenberger
Daniel Helgenberger earned 500 total points
ID: 39623555
Whitch kernel are you booting?

Note, the xen kernel in RHEL 5 only supports up to 32g; and to my knowlage you need to add the mem=32 kernel parameter there for systems with more then 32gb ram:
http://lists.centos.org/pipermail/centos/2009-December/086938.html
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Author Comment

by:nickthecomputerguy
ID: 39624624
Additional info.
I did change the parameters in the grub.conf already but used it in 96000M rather than 96G but not sure if that makes a difference.

UNAME: Linux localhost.localdomain 2.6.18-371.1.2.el5xen #1 SMP Mon Oct 7 16:38:30 EDT 2013 x86_64 x86_64 x86_64 GNU/Linux
Release: Red Hat Enterprise Linux Server release 5.10 (Tikanga)
CMDLINE: ro root=/dev/VolGroup00/LogVol00 rhgb quiet mem=92000M
BIOS ver> 6.3.0
Memory Device: 12 24 168
I had not result on State but included all mem info:
Handle 0x1000, DMI type 16, 15 bytes
Physical Memory Array
Location: System Board Or Motherboard
Use: System Memory
Error Correction Type: Multi-bit ECC
Maximum Capacity: 192 GB
Error Information Handle: Not Provided
Number Of Devices: 12
Handle 0x1100, DMI type 17, 28 bytes
Memory Device
Array Handle: 0x1000
Error Information Handle: Not Provided
Total Width: 72 bits
Data Width: 64 bits
Size: 8192 MB
Form Factor: DIMM
Set: 1
Locator: DIMM_A1
Bank Locator: Not Specified
Type: DDR3
Type Detail: Synchronous Registered (Buffered)
Speed: 1333 MHz
Manufacturer: 00AD04B380AD
Serial Number: 27542E26
Asset Tag: 01131221
Part Number: HMT31GR7CFR4A-H9
Rank: 2
DMICODE Memory: Size: 8192 MB
Size: 8192 MB
Size: 8192 MB
Size: 8192 MB
Size: 8192 MB
Size: 8192 MB
Size: 8192 MB
Size: 8192 MB
Size: 8192 MB
Size: 8192 MB
Size: 8192 MB
Size: 8192 MB
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Author Comment

by:nickthecomputerguy
ID: 39624653
I should be able to have 1TB of RAM
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Accepted Solution

by:
Daniel Helgenberger earned 500 total points
ID: 39624708
No, you are out of luck, at least without upgrading to RHEL 6:
Linux localhost.localdomain 2.6.18-371.1.2.el5xen
The XEN kernel in RHEL5 does only support up to 32G RAM
http://xen.1045712.n5.nabble.com/memory-quesion-td2609396.html

Note, this is a limitation of XEN, not RHEL
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Author Comment

by:nickthecomputerguy
ID: 39625205
How could Redhat tell me I have a 1TB limit without taking the kernel into consideration?
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LVL 13

Expert Comment

by:Daniel Helgenberger
ID: 39625270
Good question, wrong address; please forward this to RH support ;)

Try installing the mainline kernel on the host and boot it. You will see all your RAM then.

Please keep in mind the 32G limit is XEN imposed, not RH. XEN has a number of limits, maybe these are part of the reasons RH ditched XEN in favor for (IMHO the mutch better) KVM in RHEL6.

Also, print info from:
xm info

Open in new window


Also, you will find this thread very interesting:
http://grokbase.com/t/centos/centos/09c7wwpgwn/centos-5-4-x86-64-only-detects-32gb-ram-while-fedora-x86-64-correctly-lists-128gb

Particularly RH's statement:
"The Red Hat Enterprise Linux Virtualization kernel does not support more
than 32GB of memory for x86_64 systems. If you need to boot the
virtualization kernel on systems with more than 32GB of physical memory
installed, you must append the kernel command line with mem2G. This
example shows how to enable the proper parameters in the grub.conf file

And also this might help:
Supposedly, it's not an issue unless you really really want >32GB in the
Dom0 host. The Xen 64bit kernel (currently?) limits the Dom0 to 32GB.
But any guest VMs that you create will initially use the RAM not used by
the Dom0.
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Author Comment

by:nickthecomputerguy
ID: 39626310
root>  xm info

host                   : caseserver
release                : 2.6.18-371.1.2.el5xen
version                : #1 SMP Mon Oct 7 16:38:30 EDT 2013
machine                : x86_64
nr_cpus                : 8
nr_nodes               : 1
sockets_per_node       : 2
cores_per_socket       : 4
threads_per_core       : 1
cpu_mhz                : 2128
hw_caps                : bfebfbff:2c100800:00000000:00000940:029ee3ff:00000000:0                                                                                                             0000001
total_memory           : 98291
free_memory            : 63658
node_to_cpu            : node0:0-7
xen_major              : 3
xen_minor              : 1
xen_extra              : .2-371.1.2.el5
xen_caps               : xen-3.0-x86_64 xen-3.0-x86_32p
xen_pagesize           : 4096
platform_params        : virt_start=0xffff800000000000
xen_changeset          : unavailable
cc_compiler            : gcc version 4.1.2 20080704 (Red Hat 4.1.2-54)
cc_compile_by          : mockbuild
cc_compile_domain      : redhat.com
cc_compile_date        : Mon Oct  7 16:34:09 EDT 2013
xend_config_format     : 2
leopold:/root> xm info
host                   : casea.int
release                : 2.6.18-371.1.2.el5xen
version                : #1 SMP Mon Oct 7 16:38:30 EDT 2013
machine                : x86_64
nr_cpus                : 8
nr_nodes               : 1
sockets_per_node       : 2
cores_per_socket       : 4
threads_per_core       : 1
cpu_mhz                : 2128
hw_caps                : bfebfbff:2c100800:00000000:00000940:029ee3ff:00000000:00000001
total_memory           : 98291
free_memory            : 63658
node_to_cpu            : node0:0-7
xen_major              : 3
xen_minor              : 1
xen_extra              : .2-371.1.2.el5
xen_caps               : xen-3.0-x86_64 xen-3.0-x86_32p
xen_pagesize           : 4096
platform_params        : virt_start=0xffff800000000000
xen_changeset          : unavailable
cc_compiler            : gcc version 4.1.2 20080704 (Red Hat 4.1.2-54)
cc_compile_by          : mockbuild
cc_compile_domain      : redhat.com
cc_compile_date        : Mon Oct  7 16:34:09 EDT 2013
xend_config_format     : 2
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Author Comment

by:nickthecomputerguy
ID: 39626346
I guess I just didn't ask Redhat support the question correctly the first time.  I had to say RH 5.6 x86_64 WITH XEN kernel 2.6.
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Expert Comment

by:Daniel Helgenberger
ID: 39626571
So, I think there is no problem as long as you do not need more then 32G for dom0. Further, you should reduce it even more to lower dom0's footprint. Normally, you do no want the mem for your VM's; not for the XEN. If you start a guest, the memory should be deducted from the total shown there while dom0 still has 32G total.
total_memory           : 98291
free_memory            : 63658

PS: Because this happens often to me it seems. I exactly pinpointed your problem with my first comment. Therefore you should award an A to the question; even if you do not want to hear the answer. It's only fair. Please consider this in your gradings in the future.
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Author Comment

by:nickthecomputerguy
ID: 39627559
I just like the way you worded it the second time better than the first.
How do you give it a grade?
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LVL 13

Expert Comment

by:Daniel Helgenberger
ID: 39627758
In my first post I had to take a wild guess, I was asking for the kernel. Its just from my experience with XEN; though we do not use XEN any more since a long time and my knowledge is therefore not very up to date.

One thing would interest me though: In theory XEN should deduct the RAM for the guest from the total. This way, if you assign for instance 32G (the maximum) to a guest, your dom0 should still see 32G total RAM. Can you confirm this?

As for the grading, you did assign a 'B' when you should have given an 'A':
A should be the default grade awarded unless the answer is deficient. An A grade means the solution provided is thorough and informative or is a link to information that answered the question. Any links that are posted will be accompanied by a summary of what can be found there and how it helps solve the problem.
http://support.experts-exchange.com/customer/portal/articles/481419

Please do not think of me as pedantic, its just it happened several times already ;)
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