Re: [gentoo-user] Good file system that recovers from a power failure.

[Mick]

On Friday 31 December 2010 22:11:37 Volker Armin Hemmann wrote:
> reiser4 is fully atomic. A transactions happens completely or it doesn't.
>
> Unlike ext4 or btrfs or xfs.
>
> reiser4 also uses barriers (the others use them too, but), when barriers
> are not available for some reason or another, it complains in dmesg and
> goes into sync mode.
>
> This combined makes it pretty robust against power failures. You won't get
> the good old xfs/ext4/btrfs problem that a rename can end with two useless
> empty files.

I read what Volker is saying and it sounds impressive from a fs design 
perspective, but my experience does not concur with it.

I have a had a power cut (run out of battery) and the fs got corrupted.  :-(

This however may not be a conclusive finding.  I was running reiser4 for about 
a year on my laptop.  Unfortunately, I have a had a large number of fs 
corruptions, most of which appeared to be random.  The last one just before 
Christmas proved to be fatal and unrecoverable with fsck.reiser4.

I could try to blame the disk, but the MSWindows ntfs which I dual boot to 
from the same disk never failed or corrupted (admittedly though it has seen 
hardly any use).

I have to say that when it did run without corruption reiser4 is an 
exceptional fs in terms of performance.  With the exception of mounting large 
partitions which takes some time, I don't think anything else I've tried comes 
close.  If I were to build a desktop which unlike a laptop is not bounced 
around when commuting on trains and what not, I would probably try it again  
(because I have a niggling suspicion that the cause of my problems might have 
been a mechanical reason).

Either way, I can say with some certainty that power cuts and running out of 
space on a partition brought about fs corruption with reiser4.

I have now moved all but one of my partitions to ext4 and will wait to see 
what happens with that, but 11 months on reiser4 has left a bad taste in my 
mouth.

Historically, I have mostly used reiserfs and xfs.  Reiserfs is in my 
experience very reliable and easily recoverable and I can assuredly echo 
Alan's findings.  Some years ago I had a faulty memory controller which would 
hard lock an old desktop.  At least once a day (typically in the middle of an 
emerge, or updatedb) it would crash badly and I would have to pull he plug.  
In as many as 4 years I must have had hundreds and hundreds of hard reboots.  
I vaguely recall one or two fs corruptions on only one or two partitions.  
reiserfsck did recover the fs every single time without major drama.

If bleeding edge performance is not an issue I would recommend reiserfs to 
mitigate the risk from powercuts.
-- 
Regards,
Mick