What are the maximum and minimum limits for RHEL 4 vs 5 vs 6 ?

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Below chart shows you the comparison of various features of Red Hat Enterprise Linux between version 4, 5 and 6.
Version 4
Version 5
Version 6
Maximum Logical CPUs
X86
32
32
32
Itanium 2
256/512
256/1024
NA
X86_64
64/64
160/255
160/4096
POWER
64/128
128/128
128
Maximum Memory
X86
64GB
16GB
16GB
Itanium 2
2TB
2TB
NA
X86_64
256GB/1TB
1TB
3TB/64TB
POWER
128GB/1TB
512GB/1TB
2TB
Required Minimum
X86
256MB
512MB minimum/1GB/logical CPU recommended
512MB minimum/1GB/logical CPU recommended
X86_64
256MB
512MB minimum/1GB/logical CPU recommended
512MB minimum/1GB/logical CPU recommended
Itanium 2
512MB
512MB minimum/1GB/logical CPU recommended
NA
POWER
512MB
1GB minimum/ 2GB recommended
2GB minimum/ 2GB required per install
Minimum Disk Space
800MB
1GB minimum/ 5GB recommended
1GB minimum/ 5GB recommended
File systems & storage limits
Maximum filesize (Ext3)
2TB
2TB
2TB
Maximum filesystem size (Ext3)
8TB
16TB
16TB
Maximum filesize (Ext4)
---
16TB
16TB
Maximum filesystem size (Ext4)
---
1EB
1EB
Maximum filesize (GFS)
16TB/8EB *
16TB/8EB *
NA
Maximum filesystem size (GFS)
16TB/8EB *
16TB/8EB *
NA
Maximum filesize (GFS2)
---
100TB
100TB
Maximum filesystem size (GFS2)
---
100TB
100TB
Maximum filesize (XFS)
---
100TB
100TB
Maximum filesystem size (XFS)
---
100TB
100TB
Kernel and OS features
Kernel foundation
Linux 2.6.9
Linux 2.6.18
Linux 2.6.32-2.6.34
Compiler
GCC 3.4
GCC 4.1
GCC 4.4

NOTE: * 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