[mythtv-users] ext4 vs XFS for mythbuntu

Michael Heironimus mkh01 at earthlink.net
Sun Jan 25 01:35:19 UTC 2009


On Sat, Jan 24, 2009 at 11:18:50AM -0800, David Brodbeck wrote:
> Jean-Yves Avenard wrote:
> >Hi
> >
> >2009/1/22 David Brodbeck <gull at gull.us>:
> >  
> >>Kind of defeats the purpose of a journaling filesystem, but as you say,
> >>it's not a problem unique to JFS.
> >>    
> >
> >How so? > >  
> Because the main reason for using a journaling FS is to avoid having to 
> wait for long fscks to complete.  fscking a large ext2 filesystem can 
> take hours or even (in at least one case I'm aware of) days.

ext3 replays the journal at mount unless you tell it not to and fsck on
a dirty filesystem is always a full check. That means you could disable
fsck at boot, but you usually want to let it run so it can check every
few months.

XFS also replays the journal at mount. fsck on XFS is just a dummy, so
it doesn't matter if you let it run or not because it just exits.

However, the default behavior for JFS is for fsck on a dirty filesystem
to initiate a journal replay, with additional consistency checks only
running if errors are encountered. A dirty filesystem won't mount (and
you wouldn't want to mount without replaying the transaction log
anyway), so you need fsck at boot but it normally will take seconds to
run because it's just doing the same thing that XFS and ext3 do at mount
time.

-- 
Michael Heironimus


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