hardware question [2]: SATA RAID

[Stephen Ryan]

On 5/12/06, Matt Price <matt.price at utoronto.ca> wrote:
> On Fri, May 12, 2006 at 11:44:05AM -0400, Darryl Clarke wrote:
> > On 5/12/06, Matt Price <matt.price at utoronto.ca> wrote:
> > > Hi folks,
> > >
> > > space...  what I'd really LOVE to do is to have some (absolutely crucial)
> > > partitions (/home, /usr, /etc) mirrored and other, less essential partitions
> > > (/music, /videos) striped.
>
> > Based on theory, you can do exactly as you stated. :)
> >
> > If you create identical partitions on both drives, the mdadm tool can
> > be used to create the different types of raid.
> >
> > I'd try something like this:
> > sda1:sdb1 / (19gb)
> > sda2:sdb2 /home (80gb)
> > sda3:sdb3 /storage (200gb)
> > sda4:sda4 swap (1gb) * depending on your system, really...
> >
> > Then using mdadm I would create a mirror of sda1:sdb1 (md0), sda2:sdb2
> > (md1), and a stripe of sda3:sdb3 (md2), and enable both swap
> > partitions seperately
> >
> > You would effectively end up with a 19gb system, 80 gb home, and 400gb
> > of 'storage'...
>
> wow.  can I just say: linux rocks.  that is truly amazing.
>
> would it be possible to mix  this with LVM?  Say:
> sda1:sda1 (tiny)
> sda2:sdb2 (97gig)
> sda3:sdb3 (200 gig)
> sda4:sdb4 (2 gig)
>
> then set up sda1:sdb1 = md0 as /boot, mirrored
>             sda2:sdb2 = md1 as LVM containing / and /home, mirrored
>             sda3:sdb3 = md2 as LVM containing /video and /audio, striped.
> Or maybe the sda3:sdb3 wouldn't be RAID'ed at all, but just a giant LVM
>
> I guess I'm sort of thinking out loud here, os maybethe setup isn't perfect.
> but in principle does such a mixture sound plausible?

I've done something fairly close to that on a half-dozen machines and
it works pretty well.
You would need to be careful not to get mixed up (make sure you have
two separate physical volume groups, one for the mirrored partitions,
and one for the regular partitions), but that's the only problem I can
think of.  LVM might remove the need to stripe, but I don't know if
you actually get the extra performance possible from striped
configurations, or if you just get extra space, since I haven't tried
it and I ignored that part of the documentation because I was only
interested in mirroring everything.