Red Hat Enterprise Linux technology capabilities and limits

Updated -

What can Red Hat® Enterprise Linux® do? Find out in this quick-glance chart of the supported and theoretical 1 limits of the platform.

Specification Version 3 Version 4 Version 5 Version 6 Version 7
Maximum logical CPUs 2
x86 16 32 32 32 N/A6
Itanium 2 8 256 [512] 256 [1024] N/A6 N/A6
x86_64 8 64 [64] 160 [255] 448 [4096]17 768 [5120]18
POWER 8 64 [128] 128 128 768 [2048]20
System z 64 (z900) 64 (z10 EC) 64 (z13) 64 (z13) 256 (z13)
Maximum memory5
x86 64GB3 64GB3 16GB4 16GB4 N/A6
Itanium 2 128GB 2TB 2TB N/A6 N/A6
x86_64 128GB 256GB [1TB] 1TB 12TB [64TB]15 12TB [64TB]16
POWER 64GB 128GB [1TB] 512GB [1TB] 2TB 32TB21
System z 256GB (z900) 1.5TB (z10 EC) 4TB (z13) 4TB (z13) 10TB (z13)
Maximum number of device paths ("sd" devices)
256 256 13 1,024 13,14 8,192 13,14 10,000 13,14
Required minimums
x86 256MB 256MB 512MB minimum/1 GB per logical CPU recommended 512MB minimum/1 GB per logical CPU recommended N/A6
x86_64 256MB 256MB 512MB minimum/1 GB per logical CPU recommended 1GB minimum/1 GB per logical CPU recommended 1GB minimum/1 GB per logical CPU recommended22
Itanium 2 512MB 512MB 512MB/1 GB per logical CPU recommended N/A6 N/A6
POWER 512MB 512MB 1GB minimum/2GB recommended 2GB minimum/2GB required per install 2GB minimum/2GB required per install
Minimum diskspace 800MB 800MB 1GB minimum/5GB recommended 1GB minimum/5GB recommended 10GB minimum/20GB recommended
File systems and storage limits
Ext3 - Maximum file size 2TB 2TB 2TB 2TB 2TB
Ext3 - Maximum file system size 2TB 8TB 16TB 16TB 16TB
Ext3 - Maximum subdirectories 32000 32000 32000 32000 32000
Ext3 - Maximum symlink depth 8 8 8 8 8
Ext3 - ACL support Yes Yes Yes Yes Yes
Ext4 - Maximum file size -- -- 16TB 16TB 16TB
Ext4 - Maximum file system size -- -- 16TB [1EB] 16TB [1EB] 50TB [1EB]
Ext4 - Maximum subdirectories -- -- 65000/unlimited 65000/unlimited 65000/unlimited
Ext4 - Maximum symlink depth -- -- 8 8 8
Ext4 - ACL support -- -- Yes Yes Yes
GFS - Maximum file size 2TB 16TB [8EB] 16TB [8EB]7 N/A N/A
GFS - Maximum file system size 2TB 16TB [8EB] 16TB [8EB]7 N/A N/A
GFS - Maximum subdirectories -- unlimited unlimited -- --
GFS - Maximum symlink depth -- unlimited unlimited -- --
GFS - ACL support -- Yes Yes -- --
GFS2 - Maximum file size -- -- 100TB [8EB] 100TB [8EB] 100TB [8EB]
GFS2 - Maximum file system size -- -- 100TB [8EB] 100TB [8EB] 100TB [8EB]
GFS2 - Maximum subdirectories -- -- -- unlimited unlimited
GFS2 - Maximum symlink depth -- -- -- unlimited unlimited
GFS2 - ACL support -- -- -- Yes Yes
XFS - Maximum file size -- -- 100TB [8EB] 100TB [8EB] 500TB [8EB]
XFS - Maximum file system size -- -- 100TB [16EB] 300TB [16EB]19 500TB [16EB]
XFS - Maximum subdirectories -- -- unlimited unlimited unlimited
XFS - Maximum symlink depth -- -- 8 8 8
XFS - ACL support N/A N/A Yes Yes Yes
Maximum Boot LUN size (BIOS) -- -- 2TB 2TB10 2TB10
Maximum Boot LUN size (UEFI) -- -- N/A 32bit (i686) - 2TB,
64bit - 16TB (tested limit)
50TB
Maximum x86 per-process virtual address space Approx. 4GB Approx. 4GB Approx. 3GB4 Approx. 3GB4 N/A6
Maximum x86_64 per-process virtual address space 512GB 2TB 128TB 128TB
Kernel and OS features
Kernel foundation Linux 2.4.21 Linux 2.6.9 Linux 2.6.18 2.6.32 - 2.6.34 3.10
Compiler/toolchain GCC 3.2 GCC 3.4 GCC 4.1 GCC 4.4 GCC 4.8.2
Languages supported 10 15 19 22 22
NIAP/CC certified11 Yes (3+) Yes (4+) Yes (4+) Yes (4+) Under Evaluation (4+)
Common Criteria certified KVM11 -- -- Evaluated Evaluated Under Evaluation
IPv6 -- -- Ready Logo Phase 2 Ready Logo Phase 2 Under Evaluation
FIPS certified11 -- -- Yes (7 modules) Yes (8 modules) Under Evaluation (9 modules)
Common Operating Environment (COE) compliant Yes Yes N/A N/A N/A
LSB-compliant Yes - 1.3 Yes - 3 Yes - 3.1 Yes - 4.0 Under Evaluation (4.1)
GB18030 No Yes Yes Yes Yes
Client environment
Desktop GUI Gnome 2.2 Gnome 2.8 Gnome 2.16 Gnome 2.28 Gnome 3.8
Graphics XFree86 X.org X.org 7.1.1 X.org 7.4 X.org 7.7
OpenOffice V1.1 V1.1.2 V2.0.4 12 V3.2 12 LibreOffice V4.1.4 12
Gnome Evolution V1.4 V2.0 V2.8.0 V2.28 V3.8.5
Default browser Mozilla Firefox Firefox 1.5 12 Firefox 3.6 12 Firefox 24.5 12

Legend: Values are depicted as tested/supported [theoretical] above.

Notes:
1. Supported limits reflect the current state of system testing by Red Hat and its partners for mainstream hardware. Systems exceeding these supported limits may be included in the Hardware Catalog after joint testing between Red Hat and its partners. If they exceed the supported limits posted here, entries in the Hardware Catalog will include a reference to the details of the system-specific limits and are fully supported. In addition to supported limits reflecting hardware capability, there may be additional limits under the Red Hat Enterprise Linux subscription terms. Supported limits are subject to change as ongoing testing completes.
2. Red Hat defines a logical CPU as any schedulable entity. So every core/thread in a multicore/thread processor is a logical CPU.
3. The "SMP" kernel supports a maximum of 16GB of main memory. Systems with more than 16GB of main memory use the "Hugemem" kernel. In certain workload scenarios it may be advantageous to use the "Hugemem" kernel on systems with more than 12GB of main memory.
4. The x86 "Hugemem" kernel is not provided in Red Hat Enterprise Linux 5 or 6.
5. The architectural limits are based on the capabilities of the Red Hat Enterprise Linux kernel and the physical hardware. Red Hat Enterprise Linux 6 limit is based on 46-bit physical memory addressing. Red Hat Enterprise Linux 5 limit is based on 40-bit physical memory addressing. All system memory should be balanced across NUMA nodes in a NUMA-capable system.
6. Red Hat Enterprise Linux 6 does not include support for the Itanium 2 architecture. Red Hat Enterprise Linux 7 does not include support for the Itanium 2 and 32-bit x86 architectures.
7. If there are any 32-bit machines in the cluster, the maximum gfs file system size is 16TB. If all machines in the cluster are 64-bit, the maximum size is 8EB.
8. Officially support 125 CPUs across the entire machine.
9. Requires Intel EPT and AMD RVI technology support.
10. UEFI and GPT support required for more that 2TB boot LUN support (https://access.redhat.com/kb/docs/DOC-16981).
11. Get security certification details.
12. Firefox, Thunderbird, and OpenOffice applications will be updated during the life cycle.
13. Larger numbers are possible, depending on testing and support by the specific hardware vendor. For example, EMC supports up to 8,192 device paths on Red Hat Enterprise Linux 5. Consult your hardware vendor to determine their limit, and confirm with your Red Hat support representative. In no case will Red Hat support a limit that exceeds the limit supported by the hardware vendor.
14. It may be necessary to increase certain driver parameters to reach these limits. Consult with your Red Hat support representative.
15. Red Hat Enterprise Linux 6.7 is required for support of 12TB of RAM. Red Hat Enterprise Linux 6.6 can support up to 6TB of RAM. Previous versions of Red Hat Enterprise Linux 6, starting with Red Hat Enterprise Linux 6.3, support up to 3TB of RAM. Versions of Red Hat Enterprise Linux prior to Red Hat Enterprise Linux 6.3 support up to 1TB of RAM.
16. Red Hat Enterprise Linux 7.2 is required for support of 12TB of RAM. Red Hat Enterprise Linux 7.1 can support up to 6TB of RAM. Previous versions of Red Hat Enterprise Linux 7 (i.e. Red Hat Enterprise Linux 7.0) support up to 3TB of RAM.
17. Red Hat Enterprise Linux 6.7 or newer is required for 448 CPU support. The previous maximum supported CPU count for earlier versions was 288 CPUs.
18. Red Hat Enterprise Linux 7.3 with errata kernel 3.10.0-514.26.2.el7 or newer is required for 768 CPU support. Red Hat Enterprise Linux 7.2 with errata kernel 3.10.0-327.18.2.el7 or newer is required for 576 CPU support. Red Hat Enterprise Linux 7.2 or newer is required for 384 CPU support. The previous maximum supported CPU count for earlier versions was 288 CPUs. Also, for 7.2 or newer, please refer to the following Red Hat Knowledgebase article: Memory swap occurs while the pagecache is reclaimed.
19. Red Hat Enterprise Linux 6.8 or newer is required for 300TB XFS filesystem support on RHEL 6.x. The previous maximum supported XFS filesystem size in RHEL 6.7 and earlier was 100TB.
20. Red Hat Enterprise Linux 7.5 or newer, Red Hat Enterprise Linux 7.4 Extended Update Support (EUS) kernel version 3.10.0-693.25.2.el7 or newer, or Red Hat Enterprise Linux 7.3 Extended Update Support (EUS) kernel version 3.10.0-514.48.1.el7 or newer is required for 768 CPU support. The previous maximum supported CPU count for earlier update releases or EUS kernels of Red Hat Enterprise Linux 7 was 192 CPUs.
21. Red Hat Enterprise Linux 7.5 or newer, Red Hat Enterprise Linux 7.4 Extended Update Support (EUS) kernel version 3.10.0-693.25.2.el7 or newer, or Red Hat Enterprise Linux 7.3 Extended Update Support (EUS) kernel version 3.10.0-514.48.1.el7 or newer is required for support of 32TB of RAM. Previous update releases or EUS kernels of Red Hat Enterprise Linux 7 could support up to 2TB of RAM.
22. Network / PXE install requires at least 1.5 GB of RAM for the install procedure only.

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26 Comments

Very helpful information.

Very well done, indeed!

  1. Officially support 125 CPUs across the entire machine. -> to what item does this note apply?

Excellent and very useful information .

Thanks for your useful information.

May I ask what is this mean?

Maximum logical CPUs 
Specification   Version 3   Version 4   Version 5   Version 6        Version 7
x86_64                 8      64 [64]   160 [255]   240 [4096]        240 [5120]

For example, why the limit has two part of number? first 240 and second [5120]?
can you help me to understand, what is the [5120] mean?

thanks..

Hello Justin,

The first number is the tested limit, which is the maximum quantity that Red Hat's engineering and technical support teams have verified as fully functional for a given parameter. Certified systems are expected to behave correctly up to that limit. The second number is the theoretical limit, the maximum value the kernel and userspace, if applicable, should be able to support based on the current source code.

Hi,
Currently i'm using 30 days trial subscription for RHEL 6.6.
Server configuration: 2 x Xeon 6 core processor (with threading), 32 GB RAM.
Server carried high amount of network traffic, but server not take more than 55% CPU load.
I found that some CPUs are more than 80% free only 3 CPUs are 95% used.
Is trial subscription limits CPU usages/utilization?

Thanks.

Hello Rashed,
RHEL 6.6 eval subscription has no such CPU usages limitation. I suppose you should check network or your applications relevant issue or If you want to test 100% all CPU utilization on RHEL 6.6 then you can run multiple session of dd command or some other commands to generate CPU dummy load. Before this you should also ensure that the server hardware is certified with RHEL 6.6. You can use the following URL for hardware certification check on RHEL 6.
https://hardware.redhat.com/RHEL6

Best Regards
Deepak

Hi Deepak,
Thanks for your replay.
We found an issue with IRQ settings, we have changed IRQ & RPS settings & now its ok.
Thanks.

-Rashed

Thanks for the useful information

Which is the maximum LUN and physical volume size for RHEL 6 64bit?

From the point of view of the operating system, every path to a LUN is a separate device. As a result, we specify the max. number of paths that are supported (for example, 8,192 in RHEL 6). The number of LUNs will depend on the number of paths to those LUNs.

For the purpose of specifying the max. physical volume size, we use the largest supported filesystem size (100TB for RHEL 6). Although it is possible for a physical volume to have multiple filesystems (or logical volumes) on it, and the theoretical max. volume size is much larger, this limit is based on the largest volume we are able to test.

Very helpful information.

It is worth noting that minimum required RAM for normal installation via Anaconda for RHEL7 is 1 GiB but if you select all packages this can be as big as 1.5 GiB.

This seems be failing with 1 GiB with @base on RHEL 7.3 via Anaconda. I think we should change this to be at least 1.5 GiB for the RAM requirement. The same kickstart file worked fine under RHEL 7.2 with the memory at 1 GiB.

Well done fellas.

Missing the ACL limit for each filesystem

very helpful indeed.

The first row X86 Maximum logical CPUs it is listed as N/A with a note 6 note 6 talks about memory? looks like it should be note 8 8. Officially support 125 CPUs across the entire machine. this note talks about CPUs I cannot find anything on the list that has note 8 listed for note information

Actually, that note is saying that the memory number is N/A because those versions do not have a 32-bit x86 or Itanium2 version.

we are purchased the intel i3/i5 7th processor Dell/HP desktop systems, So, Im trying to install Redhat 6.5/7.4 but is is showing un supported hardware and is not entering into installation mode. kindly suggest solution

Greetings,

All certified hardware is listed in the Red hat Hardware catalog: https://hardware.redhat.com/RHEL

Please search the catalog to locate the model of interest. If it's not listed, then it may not have been certified by your favorite vendor. You can also cross reference the RHEL certification with the vendor's support website.

HTH

Ron

Red Hat Enterprise Linux 7.5+ requires 1.5 GiB as minimum amount of RAM for HTTP, HTTPS, or FTP network installation as per: https://access.redhat.com/documentation/en-us/red_hat_enterprise_linux/7/html/installation_guide/sect-installation-planning-disk-space-memory-x86

I'm sorry if this is in the wrong section but I'm having trouble installing RHEL7.5 on an Intel i7-8750H (Hexa Core) processsor. Can someone please point me to a list that shows the supported processor listing?

It is very helpful. Thank you.

Comprehensive!