Re: 2.7 thoughts

[jw schultz <jw@pegasys.ws>]

On Fri, Oct 10, 2003 at 08:29:18PM +0200, Lars Marowsky-Bree wrote:
> On 2003-10-10T08:30:03,
>    Kevin Corry <kevcorry@us.ibm.com> said:
> 
> > On Friday 10 October 2003 01:19, Stuart Longland wrote:
> > > 	- Software RAID 0+1 perhaps?
> 
> Because RAID 0+1 is a rather bad idea. You want RAID 1+0. Make up the
> fault matrix and simulate what happens if drives fail.
> 
> We can do both though, as Kevin pointed out. So if you want to shot
> yourself in the foot, in the best Unix tradition, we allow you to ;)

I concur with one caviat.  0+1 has the advantage of
extendability that doesn't exist with 1+0.

	1. break mirror downing side A
	2. break stripe A
	3. build new stripe A with added disk(s)
	4. copying stripe B to stripe A
	5. break stripe B
	6. build new stripe B with added disk(s)
	7. build mirror (A->B)

It may even be possible to do this live.  So if gradual
extendability is more important than surviving multiple
failures 0+1 has the advantage.  Normally i prefer the
reliability or to do striping at the logical volume level.


	
	


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	J.W. Schultz            Pegasystems Technologies
	email address:		jw@pegasys.ws

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