[linux-lvm] Best way to run LVM over multiple SW RAIDs?

[Stuart D. Gathman]

On Sat, 7 Dec 2019, John Stoffel wrote:

> The biggest harm to performance here is really the RAID5, and if you
> can instead move to RAID 10 (mirror then stripe across mirrors) then
> you should be a performance boost.

Yeah, That's what I do.  RAID10, and use LVM to join together as JBOD.
I forgot about the raid 5 bottleneck part, sorry.

> As Daniel says, he's got lots of disk load, but plenty of CPU, so the
> single thread for RAID5 is a big bottleneck.

> I assume he wants to use LVM so he can create volume(s) larger than
> individual RAID5 volumes, so in that case, I'd probably just build a
> regular non-striped LVM VG holding all your RAID5 disks.  Hopefully

Wait, that's what I suggested!

> If you can, I'd get more SSDs and move to RAID1+0 (RAID10) instead,
> though you do have the problem where a double disk failure could kill
> your data if it happens to both halves of a mirror.

No worse than raid5.  In fact, better because the 2nd fault always
kills the raid5, but only has a 33% or less chance of killing the
raid10.  (And in either case, it is usually just specific sectors,
not the entire drive, and other manual recovery techniques can come into
play.)

-- 
 	      Stuart D. Gathman <stuart at gathman.org>
"Confutatis maledictis, flammis acribus addictis" - background song for
a Microsoft sponsored "Where do you want to go from here?" commercial.