Linked by Rahul on Sat 18th Oct 2008 11:29 UTC
Linux While Ext4 was originally merged in 2.6.19, it was marked as a development filesystem. It has been a long time coming but as planned, Ext4dev has been renamed to Ext4 in 2.6.28 to indicate its level of maturity and paving the way for production level deployments. Ext4 filesystem developer Ted Tso also endorsed Btrfs as a multi-vendor, next generation filesystem and along with the interest from Andrew Morton, Btrfs is planned to be merged before 2.6.29 is released. It will follow a similar development process to Ext4 and be initially marked as development only.
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RE: Defragmentation
by segedunum on Sat 18th Oct 2008 17:00 UTC in reply to "Defragmentation"
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No too sure what you mean, as ext3 had no official defragmentation tool (I'm assuming you're comparing ext4 to something). It kept fragmentation to a minimum by allocating blocks that were closest to a file, but inevitably, this compromised other things and you still got fragmentation over time. This was alright in fairly static partitions such as /, /usr etc. but killed partitions with lots of file activity over time. ext4 has online defragmentation and also support for extents, which filesystems like XFS have provided for some time.

You can't break the laws of physics though. If you are going to defragment then you have to have enough free space to move all your files around, and if you don't then parts of your filesystem will simply stay fragmented with all the performance issues that entails.

However, defragmentation is merely a necessary evil with today's storage technology and you can only do so much. If SSDs kick on over the next few years and we get the same random read and write access no matter where in a storage device a file block is allocated, then fragmentation issues will start to disappear. There are actually many ways you can defragment and order data with today's mechanical disks with respect to performance. It really depends on the type of data and usage, and that's what is so difficult. Any person who tells you that a modern filesystem can solve all that is well wide of the mark.

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