OT - Journaling File Systems?

[Edwards, Scott (MED, Kelly IT Resouces)]

A few minutes ago I wrote:

> I have started wondering if it is because of write caching on the hard
> drive.

I found this article http://sr5tech.com/write_back_cache_experiments.htm
which says: "The lesson is if write back cache is turned on, it is not
difficult to create metadata inconsistency or corruption at the file
system upon power failure.". 

There are other links from that article, from the netbsd.org
http://mail-index.netbsd.org/tech-kern/2002/12/08/0031.html list:

> just to be specific, i'll post here what i told sean. having writeback
cache
> on allows the drive to delay and reorder writes. softdeps and
journaling
> fses depend on writes occurring in specific order. a drive's writeback
cache
> then obviously defeats the purpose of ordering those writes (which
softdeps
> and reiserfs, etc goto a good deal of trouble being correct).
>
> if you want *real* protection (that is, metadata consistency) you must
(on
> netbsd and linux) disable write cache. using writeback cache on the
drive,
> you're only protected from some things (accidently hit reset, kernel
panic).
> you're not protected from power failure. i have a ups, but i still
disable
> write cache. a ups can fail, and a machine's psu can fail as well.

And this from an article
http://www.linuxjournal.com/article.php?sid=4466 on ReiserFS in Linux
Journal:

> For performance benchmarks, some of the new drives have write-back
caching 
> by default. This means the drive reports a write is completed before
it 
> is actually on the media. The block is still in the drive's cache,
where 
> the writes can be reordered. If this happens, metadata changes might
be 
> written before the log commit blocks, leading to corruption if the
machine 
> loses power. It is very important to disable write-back caching on
both IDE 
> and SCSI drives. 

I have run a few tests with an old IDE drive, which had write caching
turned
off by default (I assume that wcache = 0 in /proc/ide/hda/settings means
it's
off), and I haven't been able to corrupt the FS yet.

I am going to switch now to FC2T3 and test all 4 FS's again.

Thanks for everyone's suggestions and advice.

-Scott