EXT2 file system is the predecessor to the EXT3 file system. EXT2 is not journaled, and hence is not recommended any longer (customers should move to EXT3).
EXT3
Most popular Linux file system,
limited scalability in size and
number of files
Journaled
POSIX extended access control
EXT3 file system is a journaled file system that has the greatest use in Linux today. It is the "Linux" File system. It is quite robust and quick, although it does not scale well to large volumes nor a great number of files. Recently a scalability feature was added called htrees, which significantly improved EXT3's scalability. However it is still not as scalable as some of the other file systems listed even with htrees. It scales similar to NTFS with htrees. Without htrees, EXT3 does not handle more than about 5,000 files in a directory.
ReiserFS
Best performance and scalability when
number of files is great and/or files
are small
Journaled
POSIX extended access controls
The Reiser File System is the default file system in SUSE Linux distributions. Reiser FS was designed to remove the scalability and performance limitations that exist in EXT2 and EXT3 file systems. It scales and performs extremely well on Linux, outscaling EXT3 with htrees. In addition, Reiser was designed to very efficiently use disk space. As a result, it is the best file system on Linux where there are a great number of small files in the file system. As collaboration (email) and many web serving applications have lots of small files, Reiser is best suited for these types of workloads.
To assist you with the "Why" part of your question, the Linux Gazette did an article comparing many of the filesystems used in Linux. I found the article useful although due to it's age it does lack information on "ext4".
Well, ReiserFS (and if you are up for patching your kernel, Rieser4) have some advantages, especially with small files. Unfortunately it seems they will never make it into the kernel.
At this point, I'd run ext4, unless I was paranoid, in which case I'd run ext3.
In the future, I'd run BTRFS, but that is still in alpha, it should pick up much of the niftyness of the Rieser file systems and ZFS (far and away the most interesting production file system, but not for Linux (though you can use it with FUSE)).
ReiserFS (Reiser3 / type 82 on cfdisk) is best for /var. ext4 is best for /home and if you want to change the partition size later then you need to look into LVM.
Don't use ext2 except for /boot and ext3 is a fine all-arounder, like Mario in Mario Kart.
ext3 is the standard filesystem used by operating systems based on the linux kernel.
ext4 is an "advanced" version of ext3 with various improvements, basically an upgrade to the ext3 format.
ReiserFS is another filesystem common to linux systems, but with some ongoing codebase issues whereby it periodically tries to kill your wife.
ext3 is the most common format.
Taken from: Linux Filesystem Primer
EXT2
EXT2 file system is the predecessor to the EXT3 file system. EXT2 is not journaled, and hence is not recommended any longer (customers should move to EXT3).
EXT3
EXT3 file system is a journaled file system that has the greatest use in Linux today. It is the "Linux" File system. It is quite robust and quick, although it does not scale well to large volumes nor a great number of files. Recently a scalability feature was added called htrees, which significantly improved EXT3's scalability. However it is still not as scalable as some of the other file systems listed even with htrees. It scales similar to NTFS with htrees. Without htrees, EXT3 does not handle more than about 5,000 files in a directory.
ReiserFS
The Reiser File System is the default file system in SUSE Linux distributions. Reiser FS was designed to remove the scalability and performance limitations that exist in EXT2 and EXT3 file systems. It scales and performs extremely well on Linux, outscaling EXT3 with htrees. In addition, Reiser was designed to very efficiently use disk space. As a result, it is the best file system on Linux where there are a great number of small files in the file system. As collaboration (email) and many web serving applications have lots of small files, Reiser is best suited for these types of workloads.
To assist you with the "Why" part of your question, the Linux Gazette did an article comparing many of the filesystems used in Linux. I found the article useful although due to it's age it does lack information on "ext4".
Benchmarking Filesystems
Well, ReiserFS (and if you are up for patching your kernel, Rieser4) have some advantages, especially with small files. Unfortunately it seems they will never make it into the kernel.
At this point, I'd run ext4, unless I was paranoid, in which case I'd run ext3.
In the future, I'd run BTRFS, but that is still in alpha, it should pick up much of the niftyness of the Rieser file systems and ZFS (far and away the most interesting production file system, but not for Linux (though you can use it with FUSE)).
You Should go with XFS or EXT4
ReiserFS(Reiser3/ type82oncfdisk) is best for/var.ext4is best for/homeand if you want to change the partition size later then you need to look intoLVM.Don't use
ext2except for/bootandext3is a fine all-arounder, like Mario in Mario Kart.