What is difference between Reiser FS ,EXT3 and EXT2 ?

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What is difference between Reiser FS ,EXT3 and EXT2 ?

Post by MAN6600 on Thu Jan 03, 2008 3:28 am

What is difference between Reiser FS ,EXT3 and EXT2 ?please explain the difference?which is more advantageous?

MAN6600
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Re: What is difference between Reiser FS ,EXT3 and EXT2 ?

Post by sinchuz on Sat Jan 05, 2008 2:10 am

Well friend.......

Ext2 file doesn't have journaling so it breaks easily.
Ext3 is basically ext2 plus a journal. Maybe a little slower because of it.
ReiserFS is Something Completely Different. It performs better in extreme conditions (heavy load, thousands of files in a dir etc.)

You can switch between ext2 and ext3. I don't know if there is anything that can convert between ReiserFS.

If you want performance and to look cool, go for Reiser. If you are dual booting, you will not be able to access files on a Reiser partition from Windows.

If you want to play safe and have access to your Linux files from Windows, go for Ext. If you want to write to your Linux partition from Windows, you need Ext2.

From Linux point of view, you have a choice between Ext3 and Reiser.
From Windows point of view you have the writable and easily breaking Ext2 or the read-only Ext3.
And you can convert ext2 to ext3 using the tune2fs command, these are some steps to do that
You have to make sure your kernel supports ext3 before doing that. If the kernel is anything newer than 3 years then it probably supports it.
"tune2fs -j /dev/hdxy" Will add a journal to an existing ext2 file system.

I'll post more details regarding the Linux file systems next time......

sinchuz

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Re: What is difference between Reiser FS ,EXT3 and EXT2 ?

Post by sinchuz on Sat Jan 05, 2008 2:23 am

Linux file system in detail................

Ext2

The ext2 or second extended file system is a file system for the Linux kernel. It was initially designed by Rémy Card as a replacement for the extended file system (ext). It is fast enough that it is used as the benchmarking standard. Although ext2 is not a journaling file system, its successor, ext3, provides journaling and is almost completely compatible with ext2.
The space in ext2 is split up in blocks, and organized into block groups, analogous to cylinder groups in the Unix File System. This is done to reduce external fragmentation and minimize the number of disk seeks when reading a large amount of consecutive data.

Each block group contains a super block, the group block bitmap, inode bitmap, followed by the actual data blocks.

The super block contains important information that is crucial to the booting of the operating system, thus backup copies are made in every block group of each block in the file system. However, only the first copy of it, which is found at the first block of the file system, is used in the booting.

The group descriptor stores the value of the block bitmap, inode bitmap and the start of the inode table for every block group and these, in turn is stored in a group descriptor table.
Block sizes of 8 KB are only possible on alpha-architectures by default.

EXT3

Ext3 is a journaling version of ext2. A journaling file system occupies more space and is slower than ext2.

"I understand that ext2 can easily create crashes if you do not umount a device;I don't know if this hearsay or if it is true."

If you shut down without umounting a partition then that partition should be checked and all defects fixed before you use it again. Ext2 takes longer to check and fix than either ext3 or reiserfs. The main advantage to a journaling file system is that it is easier to repair.A journal is a special part of a filesystem.

Whenever something is to be written to a journaled file system, a note is written to the journal, the new info is written to the partition, and another note is written to the journal that the write was completed. This way, your system doesn't have to check the whole partition for errors after a crash. It can just look through the journal for entries that don't have a completed note.

The ext3 file system adds, over its predecessor:

1.A journal
2.Online file system growth

There are three levels of journaling available in the Linux implementation of ext3:

Journal

(slow, but least risky) Both metadata and file contents are written to the journal before being committed to the main file system. This improves reliability at a performance penalty because all data has to be written twice. Without this setting in /etc/fstab, a file being edited in-place during a power outage or kernel panic risks being corrupted, depending on how the application is writing to the file.

Ordered

(medium speed, medium risk) Ordered is as with writeback, but forces file contents to be written before its associated metadata is marked as committed in the journal. This is the default on many Linux distributions.

Writeback

(fastest, most risky; equivalent to ext2 in some sense) Here meta data is journaled but file contents are not. This is faster, but introduces the hazard of out-of-order writes where, for example, files being appended to during a crash may gain a tail of garbage on the next mount or old files could appear after a crash. This is also how other meta data Journaling file systems do (JFS,XFS and Reiserfs)

Reiserfs

ReiserFS is a general-purpose, journaled computer file system designed and implemented by a team at Namesys led by Hans Reiser. ReiserFS is currently supported on Linux and may be included in other operating systems in the future.

ReiserFS is the default file system on the Slackware, Xandros, Yoper, Linspire, GoboLinux and Kurumin Linux[citation needed] Linux distributions. ReiserFS was the default file system in Novell's SUSE Linux Enterprise until Novell decided to move to ext3 on October 12, 2006[1] for future releases
ReiserFS offered features then unseen in existing Linux file systems:
Metadata-only journaling (also block journaling, since Linux 2.6.Cool, its most-publicised advantage over what was the stock Linux file system at the time, ext2.

Online resizing (growth only), with an underlying volume manager such as LVM. Since then, Namesys has also provided tools to resize (both grow and shrink) ReiserFS file systems offline.

Tail packing, a scheme to reduce internal fragmentation. Tail packing, however, can have a significant performance impact. Namesys recommends disabling the feature in performance-critical applications. Reiser4 may have improved this by packing tails where it doesn't hurt performance.

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Re: What is difference between Reiser FS ,EXT3 and EXT2 ?

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