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| CPG Set size change and tuning https://www.3parug.com/viewtopic.php?f=18&t=1195 |
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| Author: | sylekta [ Tue Mar 03, 2015 4:58 pm ] |
| Post subject: | CPG Set size change and tuning |
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? |
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| Author: | Schmoog [ Tue Mar 03, 2015 9:14 pm ] |
| Post subject: | Re: CPG Set size change and tuning |
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 |
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| Author: | sylekta [ Wed Mar 04, 2015 2:38 am ] |
| Post subject: | Re: CPG Set size change and tuning |
Ok thanks |
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| Author: | Architect [ Wed Mar 04, 2015 11:39 am ] |
| Post subject: | Re: CPG Set size change and tuning |
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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| Author: | afidel [ Thu Mar 05, 2015 5:00 pm ] |
| Post subject: | Re: CPG Set size change and tuning |
Architect wrote: 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. 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. |
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