Re: Docs and operation of RAID10, size limitations on 0.90

[Richard Michael <rmichael-raid@edgeofthenet.org>]

On Wed, Jul 30, 2008 at 08:29:07PM +0200, Keld Jørn Simonsen wrote:
> On Wed, Jul 30, 2008 at 12:18:06PM -0400, Bill Davidsen wrote:
> > Richard Michael wrote:
> > >Hello list,
> > >
> > >I'm building a new system with 8 disks, in two RAID5 arrays of 4 disks
> > >each, and a RAID1 array across them.  (Then LVM2 on top of the RAID1
> > >array.)
> > >
> > >I approached it this way for two reasons:
> > >
> > >1/ It feels "cleanest"; in the sense that it's not a special case, it's
> > >just RAID1 with two devices, which happen to be RAID5.
> 
> To me it seems muddy. Just having one big raid5 or raid10 would be cleaner and
> give better performance.

I can't have one big RAID5 because I want to split it in half
regularly.  I refer to it as "cleaner", because it treats the devices
separately, which is what they are; one is RAID1 device, the other is a
RAID5 device.  Each is agnostic, and independent, with regard to the
other.  "Muddy" in my opinion is a mdadm hybrid RAID10, of which I need
special knowledge.  YMMV.
 
> > >2/ I have a particular usage in mind: I need to be able to split
> > >the mirror and remove half; return it later and resync.  Therefore,
> > >I want to know which disks comprise which halves.
> 
> 
> I am not sure what you mean with this. You want to remove half of the
> disks? I think you can do that with raid10, you just remove every
> other disk. I have not tried that out, however. You could try it out
> before actually emplouing it.

Re-reading what I wrote, it's a mess of typos. :)  But, yes, I want to
remove half the disks on a regular basis, as off-site storage, and return
them to the array for periodic resync.

Regards,
Richard
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