RE: raid10 vs raid01 type in dmraid

>-----Original Message-----
>From: Heinz Mauelshagen [mailto:[email protected]] 
>Sent: Tuesday, June 26, 2007 12:58 AM
>To: Gaston, Jason D
>Cc: [email protected]; ATARAID (eg, Promise Fasttrak, 
>Highpoint 370) related discussions
>Subject: Re: raid10 vs raid01 type in dmraid
>
>On Mon, Jun 25, 2007 at 10:18:14AM -0700, Gaston, Jason D wrote:
>> >
>> >Eg, PC Magazine:
>> >"RAID 10, RAID 100 - Speed and Fault Tolerance
>> >RAID 10 is RAID 1 + 0. The drives are striped for performance 
>> >(RAID 0), and all striped drives are duplicated (RAID 1) for 
>> >fault tolerance."
>> >
>> >Yes, I konw, there's different (aargh!) definitions out there.
>> >
>> >Like I said: the top -> bottom of the stack definition is preferable
>> >to me (you reach the mirror first and the stripe second 
>while walking
>> >the stack from the top to the bottom).
>> >
>> >We just got to hold on to one definition in dmraid,
>> >
>> >Heinz
>> >
>> 
>> Ok, so the dmraid definition is not going to change.
>
>I'ld much rather avoid it :-)
>
>> 
>> Do you see an advantage in putting the RAID1 vs. RAID0 on 
>the bottom for
>> being able to perform rebuilds easier?  I need to decide 
>which way to do
>> with isw.
>
>Talking about either a mirror on top of stripes or a stripe on 
>top of mirrors,
>it is merely a question of IO minimization on rebuilds.
>
>Ie. when a stripe below a mirror breaks, you've got to 
>resilver the whole
>stripe set, hence writing 2 or more drives rather than just one disk in
>a mirror set beneath a stripe.
>
>
>With respect to ease of rebuilds at the programming level, there's no
>difference in changing the mapping of a top level mirror to do a full
>resync vs. a bottom level mirror.
>
>
>Getting back to your decision: you could support both ;-)
>
>Cheers,
>Heinz
>
>> 
>> Thanks,
>> 
>> Jason
>

After adding support for RAID10 to isw.c, what will we need to do in
order for this to be supported in anaconda, so that we can install to a
RAID10 nested volume?  I don't see support for nested RAID levels in
dmraid.py.

Thanks,

Jason