EXT3 on raid with external journal...

Matt Bernstein mb/ext3 at dcs.qmul.ac.uk
Wed Apr 14 09:06:08 UTC 2004

On Apr 13 Kurt Fitzner wrote:

>I have a raid5 array on my web server for which I am currently 
>considering a move to ext3.  I want to use an external journal to 
>improve performance.
>Since the external journal would reside on a drive  that is not 
>participating in the raid array, I'm wondering what the behavior of an 
>ext3 filesystem is should the device an external journal is on should 
>fail.  If it reverts to ext2 behavior upon failure, then I can justify 
>using a non-raid device for an external journal.

There could be metadata which is only in the journal, so failure probably 
means reboot + full fsck, so you may as well use ext2 if your machine 
doesn't otherwise crash.

Far preferable, I think, would be to put your journal on a RAID 1 pair.

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