EXT4 vs XFS: large volumes with high-end RAID controller

Written by Gionatan Danti on . Posted in Linux & Unix

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Fragmentation

Fragmentation is the #1 enemy of mechanical disks, as every head movement correspond to lower total I/O performance.

Both EXT4 and XFS has a fame to be very fragmentation resistant, but what is the best?

Let's start with counting fragments per file after the extraction of the Linux kernel .tar.bz2 file (see the untar test above for more informations):

EXT4 vs XFS

Yeah, both filesystems where exceptionally resistant to fragmentation here, showing perfect results.

Sysbench's sequential and random tests give us another interesting point of reference in this discipline. First, the fragmentation status after the sequential write test:

EXT4 vs XFS

Now XFS is the leader, with EXT4 lagging quite behind. It is interesting to note that in the synchronous test (one write / one fsync) EXT4 exhibits lower fragmentation: this can explain the higher sequential read results in synchronous mode recorded earlier. Speaking about XFS, it seems that this filesystem optimally manage large files and its high sequential read/write speeds are likely a results of the complete lack of fragmentation in these class of files.

The random write test now:

EXT4 vs XFS

In this case, both filesystems become heavily fragmented, proving that no filesystem is completely immune to this issue. However, XFS has and edge here: it ships with a functional, proven defragmenter, while the EXT4 package lack an official, stable-released defrag utility (while this utility exists, it is more-or-less in a beta stage).

Comments   

 
#1 Evgeny 2012-12-10 07:21
it's looks that you fsck time ext4 isn't true.
I think that you ran fsck.ext4 /dev/sd__something__
without "-f" key. It's means that fsck FS state
tune2fs -l
...
Filesystem state: clean
...
and if it clean do nothing
 

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