RAID 1+0

[Tony Holmes]

On +Aug 22, Mathew Kanner wrote:
> 
> 	Hello Tony,
> 	I've just recently trashed a vinum raid10 volume by loosing
> two disks.  So, yes it is possible in vinum, look for "RAID-10" in the
> manual.

That's what I would call RAID-0+1 (mirroring stripes).

Ie. plex A = 1 + 2 striped
    plex B = 3 + 4 striped

    volume = A + B mirrored

	Dead Drive Chart - if these drives die, how is data?

	Drive	1	2	3	4
	1	OKAY	OKAY	DEAD	DEAD
	2	OKAY	OKAY	DEAD	DEAD
	3	DEAD	OKAY	OKAY	OKAY
	4	DEAD	DEAD	OKAY	OKAY

    ie. 50% of the cases you can recover (drive 1 and 1 dying is single drive)

What I'm looking for is RAID-1+0 (striping mirros)

Ie. plex A = 1 + 2 mirrored
    plex B = 3 + 4 mirrored

    volume = A + B striped


	Drive	1	2	3	4
	1	OKAY	DEAD	OKAY	OKAY
	2	DEAD	OKAY	OKAY	OKAY
	3	OKAY	OKAY	OKAY	DEAD
	4	OKAY	OKAY	DEAD	OKAY

    ie. 75% of the cases you can recover

For the RAID 1+0 case you require both drives of the same mirror
to die to lose your data.

Given vinums configuration file, we'd need something like the following
that is not supported (just to help you visualize).

drive d1 device /dev/da1e
drive d2 device /dev/da2e
drive d3 device /dev/da3e
drive d4 device /dev/da4e
volume raid10 setupstate
  plex org striped 512k
    subplex org concat
	sd length 512m drive d1
    subplex org concat
	sd length 512m drive d2
  plex org striped 512k
    subplex org concat
	sd length 512m drive d3
    subplex org concat
	sd length 512m drive d4



-- 
Tony Holmes

Founder and Senior Systems Architect
Crosswinds Internet Communications Inc.