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RAID 1 (4D+4D) on XP arrays

Nigel Poulton
Respected Contributor

RAID 1 (4D+4D) on XP arrays

Is there any different between the way that RAID 1 (4D+4D) is implemented on the xp1024 and the xp12000?
I know that in the Storage Navigator (CommandView) GUI on the xp1024 all 4D+4D concatenated groups show up as 2D+2D but you can view the concatenation list and see that the RGs are actually concatenated on the back end. Ive heard varying responses to the from different people (HDS and HP) and may be I will here too ;-)
But its worth asking - thanks!
Talk about the XP and EVA @ http://blog.nigelpoulton.com
6 REPLIES
Chris Callihan_1
Frequent Advisor

Re: RAID 1 (4D+4D) on XP arrays

on the 1024, 4D+4D was actually 2 x 2D+2D concatenated

on the 12000, 4D+4D is actually 4D+4D
Nigel Poulton
Respected Contributor

Re: RAID 1 (4D+4D) on XP arrays

Thanks for the response Chris.

Just to be clear - you are saying that on the XP1024 a 4D+4D is just a 2 concatenated 2D+2D's. As such you will fill up one half of the concatenation set first (on one ACP) and then only start using the spindles in the second half after the first half is full?

And finally, not that I dount your answer at all ;-) how sure are you about this as Ive heard varying responses on this topic in the past.
Talk about the XP and EVA @ http://blog.nigelpoulton.com
Kamel Abada_2
Occasional Contributor

Re: RAID 1 (4D+4D) on XP arrays

Hi,

Can anyone confirm this, I would also like to know the answer.

Many thnaks

Kamel
Seref Tufan SEN
Occasional Advisor

Re: RAID 1 (4D+4D) on XP arrays

Hi ,

We are using XP12000 and HP had told us that 4D+4D is just two 2D+2D concatenated. I'm confused now :)
Robert Dobalina
Valued Contributor

Re: RAID 1 (4D+4D) on XP arrays

A 4D+4D on a 12K is a two concatenation of RAID1 (2D+2D). The data is written across all 4 Raid Pairs. So data A B C D is written to each raid pair which the writes to its mirror.

A 1024 on the other hand does fill one then the other.

Patrick Terlisten
Honored Contributor

Re: RAID 1 (4D+4D) on XP arrays

Hello,

a 4D+4D on a 1024 contains two 2D+2D, but the two 2D+2D will filled consecutively? A 12k will write across the two 2D+2D, so that I will get better peformance (four disks will used, instead of two). Is this right?

Regards,
Patrick
Best regards,
Patrick