Questions regarding journal replay

Eric Sandeen sandeen at
Wed Feb 25 17:44:10 UTC 2009

Ralf Hildebrandt wrote:
> * Theodore Tso <tytso at>:
>> On Wed, Feb 25, 2009 at 10:31:42AM -0600, Eric Sandeen wrote:
>>> It'd be better to get to the bottom of the problem ... maybe iostat
>>> while it's happening to see if IO is actually happening; run blktrace to
>>> see where IO is going, do a few sysrq-t's to see where threads are at, etc.
>>> Can you find a way to reproduce this at will?
>>> Journal replay should *never* take this long, AFAIK.
>> Indeed.  The journal is 128 megs, as I recall.  So even if the journal
>> was completely full, if it's taking 800 seconds, that's a write rate
>> of 0.16 Mb/S (164 kb/second).   That is indeed way too slow.  
> The problem seems to be with the external journal which I recently
> changed to. It's a 32GB partition. My timings seem to indicate that
> ALL OF IT was being replayed

But you also saw this with an internal journal?

Perhaps you have uncovered 2 bugs ... :)

TBH external journals probably aren't tested that much (though they
certainly should work)

I'll give it a quick sanity test on ext4.


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