Troubleshooting
Problem
Red Hat Enterprise Linux 5 (RHEL5) is strictly limited to 1 Terabyte (TB) or less of physical memory addressing and will not report or use any memory above 1 TB of physical addressing. Memory reported above 1 TB that cannot be used by RHEL5 can be in the following two (2) forms: 1. Physically installed memory array larger than 1 TB such as 1.5 TB. 2. Reclaimed/remapped memory appended to the end of the physical memory when 1 TB is installed (this is memory that is typically behind the Peripheral Component Interconnect (PCI) MMIO hole below 4 gigabytes (GB) and is reclaimed/remapped up high).
Resolving The Problem
Source
RETAIN tip: H197026
Symptom
Red Hat Enterprise Linux 5 (RHEL5) is strictly limited to 1 Terabyte (TB) or less of physical memory addressing and will not report or use any memory above 1 TB of physical addressing.
Memory reported above 1 TB that cannot be used by RHEL5 can be in the following two (2) forms:
- Physically installed memory array larger than 1 TB such as 1.5 TB.
- Reclaimed/remapped memory appended to the end of the physical memory when 1 TB is installed (this is memory that is typically behind the Peripheral Component Interconnect (PCI) MMIO hole below 4 gigabytes (GB) and is reclaimed/remapped up high).
Affected configurations
The system is configured with at least one of the following:
- Red Hat Enterprise Linux 5, any update
This tip is not system specific.
This tip is not option specific.
Note: This does not imply that the network operating system will work under all combinations of hardware and software. Please see the compatibility page for more information: http://www.ibm.com/servers/eserver/serverproven/compat/us/
Additional information
The Red Hat web site is a bit confusing as it states that RHEL5 supports both "unlimited" and "1 TB" under different sections of its comparison page. RHEL5 is internally limited to 1 TB and users and support should reference the "Maximum memory" subsection of the "Technology capabilities and limits" section of the comparison page, which states 1 TB as the theoretical limit. The theoretical limit listed of 1 TB is also the empirically proven physical limit the Operating System (OS) can address.
For more information, refer to the "Red Hat Enterprise LinuxServer Version comparison chart," available at the following URL:
| http://www.redhat.com/rhel/compare/ |
Document Location
Worldwide
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Document Information
Modified date:
30 January 2019
UID
ibm1MIGR-5084203