choosing a file system

[Adam Tauno Williams]

On Wed, 2008-12-31 at 15:46 +0200, Janne Peltonen wrote:
> On Wed, Dec 31, 2008 at 07:38:21AM -0500, Adam Tauno Williams wrote:
> > In regards to ext3 I'd pay attention to the vintage of problem reports
> > and performance issues;  ext3 of several years ago is not the ext3 of
> > today, many improvements have been made.  "data=writeback" mode can help
> > performance quite a bit, as well as enabling "dir_index" if it isn't
> > already (did it ever become the default?).  The periodic fsck can also
> > be disabled via tune2fs.   I only point this out since, if you already
> > have any ext3 setup,  trying the above are all painless and might buy
> > you something.
> I wouldn't call data=writeback painless. I had it on in the testing phase
> of our current Cyrus installation, and if the filesystem had to be
> forcibly unmounted by any reason (yes, there are reasons), the amount of
> corruption in those files that happened to be active during the unmount
> - well, it wasn't a nice sight. And the files weren't recoverable,
> except from backup.
> 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.