3PAR 7200C Mixed hard drive capacity

[YAKEN]

Hi 

      I have Cage0 (300GB  , 15K,FC,SAS) *24 , Cage1 (600GB , 15K,FC,SAS)*24 , can I use CPGS cross this two  Cages , have any performance issue ? thanks

[Sheldon Smith]

From what little you say, it sounds like you started with a 7200c with 24 300GB drives. Then later have added a second cage with 24 600GB drives. Correct?

From a basic performance standpoint, you can have a CPG with all 48 drives in it. With all 48 drives, you will get better performance than with just the original 24. And, unless you have drive pattern filters on your CPGs, they already do use all 48 drives. Hopefully, when the second cage was added, tunesys was run one or more times to distribute what was on the original 24 drives across the 48 drives. Which would have improved the performance of any existing volumes. If not, any volumes created when you had the original 24 300GB drives will still be on just those 24.

What you need to be aware of is, all 48 drives are going to fill fairly evenly. When the 300GB drives fill up, any storage allocation after that time will of course be only on the 600GB drives. Performance on that portion of storage will be reduced compared to any volumes (technically Logical Disks) that are built across all 48 drives.

You can create a CPG that uses just the drives in Cage1. Put any volumes that do not need the improved performance there; this will at least delay the 300GB drives from filling up. For example: createcpg -p -cg 1 -ha mag -t r5 FC_r5_600GB

For each volume you want in the new CPG you will need to:

1. Create a new matching volume in the new CPG,
2. present the new volume to your host, and
3. have the host copy everything from the old volume to the new volume. Which will mean stopping any application(s) using that volume while you are moving everything. If the application(s) use multiple volumes, you would need to have a matching new volume for each of them.
4. Then unexport both the new and the old, and
5. export the new back out with the LUN of the old volume. So the new volume takes the place of the old.
6. Check the applications work correctly, and
7. finally delete the old volume.

If you have a Dynamic Optimization license, you can avoid all of that and use tunevv to move volumes into the new CPG with no "down" time.