[CentOS] LVM RAID0 and SSD discards/TRIM

Tue Aug 20 10:39:30 UTC 2013
Mihai T. Lazarescu <mtlagm at gmail.com>

On Tue, Aug 20, 2013 at 12:20:01PM +0200, Dennis Jacobfeuerborn wrote:

> On 19.08.2013 20:28, Joakim Ziegler wrote:
> > I'm trying to work out the kinks of a proprietary, old, and clunky
> > application that runs on CentOS. One of its main problems is that it
> > writes image sequences extremely non-linearly and in several passes,
> > using many CPUs, so the sequences get very fragmented.
> >
> > The obvious solution to this seems to be to use SSDs for its output, and
> > some scripts that will pick up and copy our the sequences in proper
> > order once it's done. I have two 512GB SSDs, and I've used LVM to set up
> > a RAID0 between them.
> >
> > I've got that part running, but since I'm on CentOS 5.8 (which is what
> > this application officially supports), I don't have a kernel with SSD
> > discard support, and after a few days (I told you, this application is
> > write intensive), things get very slow.
> >
> > Using hdparm to secure erase the drives and recreating the LVM RAID0
> > gets things back to speed again, but that's obviously not ideal.
> >
> > So, from what I understand, if I can get this thing running on CentOS
> > 6.4, I'll get kernel discard support, and discard support in LVM when
> > running a RAID0. I'm using ext4.
> >
> > Is that correct? Will this solve my problem? I want to confirm that
> > discard support works on a RAID0 of SSDs using LVM and ext4 before I
> > start working on getting this legacy application to run on a newer CentOS.
> What kind of SSD are you using?  We use Intel 520's here
> and don't really see these kind of slowdowns.

You can also check a newer kernel for CentOS 5 from ELrepo: