Linux – Questions for Ext3/4 Features ( dir_index,filetype) and XFS File system Performance

ext3ext4filesystemslinuxxfs

I am developing an applications which reads huge list of directories and check file types using file command and using ext4 file system.

When i look into Ext4 , i see it have two interesting features

  • dir_index
  • filetype

i just enabled both features using 

tune2fs -O dir_index /dev/hdXY 
e2fsck -fD /dev/hdXY

my questions are :

  1. Is dir_index works transparently after it is enabled , (ie. ls -lR large_direcory/ performance improved without need for any extra program/config) or have to make it work via programming/scripting?
  2. Indexes are generated transparently ? or need to regenrated using e2fsck -fD /dev/hdXY?
  3. How does Ext3/4 filetype feature works?
  4. I have read XFS have better performance and Reliability over ext3 , how does it compare to ext4 , should i switch?

Thanks!

Best Answer

Answer to your fourth question, or at least something worth thinking:

One thing where XFS shines compared to ext3 (maybe also ext4) is concurrency. XFS scales nicely in multi-processor environment, but with ext3 kjournald does not utilize multiple cores very well.

So if several processes are fighting for disk access simultaneously, then XFS is a very good choice. I think ext4 also gained allocation groups so it might make it better with SMP, too, but that's one thing to keep in mind while benchmarking.

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