[linux-lvm] LVM and sw RAID1

[Ragnar Kjørstad]

On Thu, Aug 24, 2000 at 08:04:38PM +0200, Luca Berra wrote:
> > > fixed that and pvmoved everything onto my lvm+raid5 (fixing another bug
> > > in the process).  Well, i discovered that reiserfs + LVM + raid DOES NOT
> > > WORK, it actually filled 95% of my files with zeroes :)
> > 
> > No journalling filesystem will work properly with RAID 5 - not reiserfs
> > and not ext3.  You need to stick with a non-journalling filesystem, or
> > use RAID1.  It may be that this is supposed to be fixed in 2.4, but I'm
> > not 100% sure...
> > 
> I probably dinna specify but it i am running 2.4.0-test7pre5
> so i can confirm reiserfs not working on raid+lvm with 2.4

If you have more information, please send a bugrapport to
reiserfs at devlinux.com.

> AFAIR the problem with journaling and raid was due to raid's usage
> of the buffer cache during recnstruction, there was no reconstrucion
> happening on my system. i will also try reiserfs on raid without
> lvm, i cannot try ext3 since there isn't any patch for 2.4

For linux 2.2 it will not work with raid5 at all, the reconstruction
issue is just for mirroring....I think.

>From Chris Mason on reiserfs at devlinux.com:

> reiserfs and raid:
> The FAQ should state that hardware RAID is not a problem
> 2.2: I found a mail saying that concatening, striping and mirroring
>      are ok, but raid5 has issues, but I also seem to remember reading
>      there were issues with reconstructing mirroring?

Correct, any hardware raid is safe.  For software, striping is ok.
Mirroring is ok, but you *cannot* use the online mirror rebuild.
software raid5 is unsafe.  lvm is safe.

> 2.4: Is everything working here? both lvm and md?
>
Yes, software raid in 2.4 is working properly, and so is lvm.


-- 
Ragnar Kjorstad
Torque Systems / Big Storage