Thursday, February 2, 2012

Features Comparison: Ext3 vs Ext4

Here is the quick facts and comparison of Ext3 and Ext4 File systems:  Hope this helps..!

Stands For
Ext3 stands for third extended file system.
Ext4 stands for fourth extended file system.
It was introduced in 2001.
It was introduced in 2008.
Kernel Support
Supports from Linux Kernel 2.4.15
Supports from Linux Kernel 2.6.19
Maximum individual file size supported
Maximum individual file size can be from 16 GB to 2 TB
Maximum individual file size can be from 16 GB to 16 TB
Maximum file system size supported
Overall ext3 file system size can be from 2 TB to 32 TB
Overall maximum ext4 file system size is 1 EB (exabyte).
1 EB = 1024 PB (petabyte).
1 PB = 1024 TB (terabyte).
Maximum sub directories
Directory can contain a maximum of  32,000 subdirectories
Directory can contain a maximum of 64,000 subdirectories
Other Features
The main benefit of ext3 is that it allows journaling. 

Journaling has a dedicated area in the file system, where all the changes are tracked. When the system crashes, the possibility of file system corruption is less because of journaling.

There are three types of journaling available in ext3 file system.

Journal – Metadata and content are saved in the journal.

Ordered – Only metadata is saved in the journal. Metadata are journaled only after writing the content to disk. This is the default.

Writeback – Only metadata is saved in the journal. Metadata might be journaled either before or after the content is written to the disk.
In ext4, it supports journaling and also has the option of turning the journaling feature “off”.

Several other new features are introduced in ext4: multi block allocation, delayed allocation, Journal checksum, fast fsck and etc.

All you need to know is that these new features have improved the performance and reliability of the file system when compared to ext3.

Supports huge individual file size and overall file system size.

You convert ext2 to ext3 without having any data loss
You can also mount an existing ext3 fs as ext4 fs (without having to upgrade it).