HPE Storage Users Group

Hi


Can you change the set size of a CPG with active virtual volumes in it?

I have PD space issue and my primary CPG is R5 with 2-1 set size. If I say change this to an 8-1, in theory I have far less parity chunklets so am I freeing up space? Would this also increase performance?

What about tuning on the fly, can I do the tuning calculation and change my growth increment based on new set size and will it re-stripe across my disks?

No guarantees, but I'm pretty sure you can't change the set size...

Even if you could, you wouldn't want to because the data layout on disk would be less than ideal after the change.

In order to do this, you would create a new cpg with the correct set size, then use DO to tune the vv's to the new cpg

Ok thanks

well, actually you can.

all new LDs would then be created according to the new parameters, and you would need to tune the CPG to restripe the old LDs to new ones with the new parameters.

not tuning would create an interesting mess, where volumes would be sitting on a mix of different LD types.

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The goal is to achieve the best results by following the clients wishes. If they want to have a house build upside down standing on its chimney, it's up to you to figure out how do it, while still making it usable.

I actually had this happen, the tier-3CPG's in our primary AO policy had FC R6 as the config instead of the intended NL R6 and so we ran too low on FC space to perform our rebalance when we did our node expansion. I changed the CPG and tuned some of the vvols to a new CPG to immediately free up space so we could do the expansion, and then tunesys moved everything else over the course of several months but all of the vvols that I didn't immediately tune continued to have a mixed LD structure until the tunesys completed, including some that had both FC-R6 and NL-R6 in their tier-3, it did not cause any issues.