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 Post subject: CPG Question
PostPosted: Wed Dec 21, 2011 2:28 pm 

Joined: Wed Dec 21, 2011 1:37 pm
Posts: 4
So I am relatively new to the 3PAR world with experience with other vendors. I have a question on laying out CPGs. First off I have been looking for documentation on Best Practices for CPG creation. I found documents for Exchange and other platforms but looking for a general Best Practices.

I have a couple of other questions specific to CPG creation. Environment; We currently have a S800 with 8 nodes, 23 Cages, and 848 spindles.

1. Does the Set Size really matter on a CPG because of the virtualize nature of the array? We utilize Raid 5 (2.2.4) with a default Set Size of 3+1. In traditional arrays, the Set would have better performance with say a 8+1. Our SE is saying it really doesn't matter.
2. Does anyone have a good rule to layout the CPG for performance with High Availability in mind. As a default, we use Cage Availability but traditionally used Fully Allocated Volumes from PD utilizing a Template. We are moving to TPVV so require CPGs.
3. Can magazines be shared by multiple CPGs or once filtered be exclusive to that CGP.

TIA


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 Post subject: Re: CPG Question
PostPosted: Fri Dec 23, 2011 4:44 pm 

Joined: Mon Dec 12, 2011 5:08 am
Posts: 77
I think you would get the best performance if you run 8+1 , at least if your running Raid5.

From the Documentation:

On a RAID 50 logical disk, data is striped across rows of RAID 5 sets. A RAID 5 set, or parity set,
must contain at least three chunklets. A RAID 5 set with three chunklets has a total of two
chunklets of space for data and one chunklet of space for parity. RAID 5 set sizes with between
3 and 9 chunklets are supported. The data and parity steps are striped across each chunklet in
the set. The chunklets in each RAID 5 set are distributed across different physical disks, which
may be located in different drive magazines or even different drive cages. The number of sets
in a row is the row size. The system accesses the data from a RAID 50 logical disk in step sizes.
The step size is the number of contiguous bytes that the system accesses before moving on to
the next chunklet. A RAID 5 set can function with the loss of any one of the chunklets in the
set.

3. Can magazines be shared by multiple CPGs or once filtered be exclusive to that CGP

If you filter them out and only add certain disk to a CPG , then you can still use them in another CPG if you don't filter it out on that one.

But all in all I think you would just make more work for yourself if you start to filter out CPG from certain disks.


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