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

["Keld Jørn Simonsen" <keld@dkuug.dk>]

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.

> >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.

> >However, I'm rethinking toward RAID10.  However, I can't find much
> >documentation about layout, etc.  I believe this was recently discussed
> >on the list.

There is documentation on http://linux-raid.osdl.org/
and on http://std.dkuug.dk/keld/stripemirror.html (for raid10,f2), and 
on http://en.wikipedia.org/wiki/Non-standard_RAID_levels


Best regards
keld