choosing a file system

Henrique de Moraes Holschuh hmh at
Sat Jan 3 09:45:19 EST 2009

On Wed, 31 Dec 2008, Adam Tauno Williams wrote:
> > I never really got the point of the data=writeback mode. Sure, it
> > increases throughput, but so does disabling the journal completely, and
> > seems to me the end result as concerns data integrity is exactly the
> > same.
> The *filesystem* is recoverable as the meta-data is journaled.
> *Contents* of files may be lost/corrupted.  I'm fine with that since a
> serious abend usually leaves the state of the data in a questionable
> state anyway for reasons other than the filesystem;  I want something I
> can safely (and quickly) remount and investigate/restore.  It is a
> trade-off.

Err... you guys better read the recent threads in LKML where Pavel goes
really hard on the data safety holes in ext3 and Linux VFS (and POSIX).

Short answer: ext3 without barriers (you can also disable disk write cache,
in that case barriers are not needed) is not deserving of the name "safe".
At which point *I* personally prefer XFS, which is just as adverse to the
lack of barriers on a disk with an enabled write cache, but performs better
than ext3 on most workloads AND has delayed write allocation.

Ext4, I never tried.  Nor reiser3.  I may have to, we will build a brand new
Cyrus spool (small, just 5K users) next month, and the XFS unlink
[lack of] performance worries me.

  "One disk to rule them all, One disk to find them. One disk to bring
  them all and in the darkness grind them. In the Land of Redmond
  where the shadows lie." -- The Silicon Valley Tarot
  Henrique Holschuh

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