Supported system configurations and limits for Red Hat Enterprise Linux releases

Red Hat Enterprise Linux releases are released on a predictable 18 month schedule, and supported for seven years from their date of initial availability. Under the standard Red Hat Enterprise Linux subscription, customers are free to use any version and may upgrade at any time for no additional charge.

Red Hat Enterprise Linux release dates are as follows:

Version 2.1 - May 2002
Version 3 - September 2003
Version 4 - February 2005

While each release provides many compelling new features, some customers will wish to continue to use earlier versions for a variety of reasons:

To maintain an identical user, administration and application environment as existing systems.
When a new version is released it is likely that earlier releases will have more extensive ISV application and OEM hardware certifications. Red Hat works closely with its ISV/OEM partners to ensure that their products are certified as soon as possible on each new version, but it generally takes a few months before the same level of certification as earlier versions is achieved. View the latest ISV application and OEM hardware certifications for both Red Hat Enterprise Linux versions.
Some organizations have centralized product approval processes which may not have been updated to authorize use of the latest release.

The following list outlines the major differences and similarities between Red Hat Enterprise Linux versions 2.1, 3 and 4:

	Version 2.1	Version 3	Version 4
Architecture support
Supports x86 systems	Yes	Yes	Yes
Supports Itanium2 systems (1)	Yes	Yes	Yes
Supports AMD64/EM64T systems	No	Yes	Yes
Supports IBM POWER, zSeries & S/390 systems	No	Yes	Yes
Support limits as defined by Red Hat Enterprise Linux Product Subscription
AS system limits (all architectures):
Maximum physical CPUs (2)	-	-	-
Maximum memory	-	-	-
ES system limits (all architectures) (3):
Maximum physical CPUs (2)	2	2	2
Maximum memory	4GB	8GB	16GB
WS system limits (all architectures) (3):
Maximum physical CPUs (2)	2	2	2
Red Hat Desktop limits (all architectures) (3):
Maximum physical CPUs (2)	n/a	1	1
Maximum memory	n/a	4GB	4GB
Technology limits (certified[/theoretical]) (7)
Maximum logical CPUs (4)
x86	8	16	32
Itanium2	4	8	64/512
AMD64/EM64T	n/a	8	64/64
Power	n/a	8	64/128
zSeries	n/a	8	8
Maximum memory
x86 (6)	16GB	64GB	64GB
Itanium2	32GB	128GB	256GB/1024TB
AMD64/EM64T	n/a	128GB	128GB/1TB
Power	n/a	64GB	128GB/1TB
zSeries	n/a	64GB	64GB
Maximum filesize	1TB	1TB (5)	8TB
Maximum filesystem size (Ext3)	1TB	1TB (5)	8TB
Maximum x86 per-process virtual address space	3GB	Approx 4GB	Approx 4GB
Required minimums
Minimum memory
x86	256M	256M	256M
Other architectures	512M	512M	512M
Minimum diskspace	500M	800M	800M
Kernel & OS features
Kernel foundation	Linux 2.4.9	Linux 2.4.21	Linux 2.6.9
Compiler/toolchain	GCC 2.9.6	GCC 3.2	GCC 3.4
Languages supported	4	10	15
Selectable I/O schedulers	No	No	Yes
Internet/Intranet Input Method support	No	No	Yes
Sys_epoll support	No	No	Yes
SELinux	No	No	Yes
Ext3 Performance Enhancements	No	No	Yes
SCTP support	No	No	Yes
Bluetooth support	No	No	Yes
GCC Buffer Bound Checking	No	No	Yes
Glibc Memory Corruption Checking	No	No	Yes
Exec Shield, PIE, NX/XD support	No	Yes	Yes
Native POSIX Threading Library	No	Yes	Yes
Hyperthreading scheduler	No	Yes	Yes
Autofs V4	No	Yes	Yes
NIAP/CC certified	No	Yes - 3+	In progress - 4+
Logical Volume Manager	No	Yes - LVM1	Yes - LVM2
Reverse Map VM	No	Yes	Yes - enhanced
Auditing	No	Yes - LAus	Yes - audit
Compatibility libraries	No	Yes - 2.1	Yes - 2.1 & 3
Asynchronous I/O for storage devices	Yes	Yes	Yes
CoE compliant	Yes	Yes	Yes
LSB compliant	Yes - 1.2	Yes - 1.3	Yes -1.3 (3 in progress)
NFS	Yes - V3	Yes - V3	Yes - V3 & V4
Client environment
Desktop GUI	GNOME 2.0	Gnome 2.2	Gnome 2.8
Graphics	XFree86	XFree86	X.org
OpenOffice	No	Yes - 1.1	Yes - 1.1.2
Ximian Evolution	No	Yes - 1.4	Yes - 2.0
Default browser	Netscape	Mozilla	Firefox
Multimedia capabilities	No	No	Yes
Plug and play	No	No	Yes
Layered products
Supports Red Hat Cluster Suite	Bundled with AS, not available for ES	Yes	Yes
Supports Red Hat Global File System	No	Yes	Yes
Supports Red Hat Developer Suite	No	Yes	Yes
Supports Red Hat Application Server	No	Yes	Yes

(1) Itanium2 only; the original Intel Itanium processor is not supported.

(2) Red Hat defines physical CPUs equivalently to sockets, so a multi-core and/or hyperthreading CPU is counted as a single CPU or socket when determining whichedition of Enterprise Linux to deploy.

(3) All other limits for Enterprise Linux ES, WS, and Desktop are the same as for AS.

(4) Red Hat defines logical CPUs equivalent to cores/virtualCPUs, so a dual-core (non-hyperthreading) CPU is counted as 2 logical CPUs and a single hyperthreading CPU is counted as 2 logical CPUs.

(5) As of Red Hat Enterprise Linux 3 U5, the maximum filesize and maximum filesystem size is 2TB.

(6) 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.

(7) Please note that limits for Red Hat Enterprise Linux v4 are for Update 3 or later. Update 3 was released in March 2006. CPU counts over 8 (AMD64/EM64T) or 64 (other architectures) require use of the largesmp kernel. Certified limits reflect the current state of system testing by Red Hat and its partners, and the limit of support provided by a Red Hat Enterprise Linux subscription.

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