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Multipe AO groups on the same disks
https://3parug.com/viewtopic.php?f=18&t=2790
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Author:  InteraX [ Mon Feb 05, 2018 5:43 am ]
Post subject:  Multipe AO groups on the same disks

We have added some more disk space to our systems and are going to re-create our AO CPGs so we can modify the step size to reflect the number of disks and set size in each tier.

Should we stop our current AO tasks/schedules or can we have both AO tasks running at the same time? If we have 2 AO tasks trying to run concurrently, will they conflict?

Author:  MammaGutt [ Mon Feb 05, 2018 2:44 pm ]
Post subject:  Re: Multipe AO groups on the same disks

You could be "lazy" and simply edit your existing CPG and run tunesys. That way you don't need to tune all your volumes to a new CPG and wait for AO to push data up and down again.

You should stop AO while running that type of tunesys because there is a good chance they may conflict on some blocks leaving some LDs with the old set size.

Author:  InteraX [ Fri Feb 09, 2018 6:10 am ]
Post subject:  Re: Multipe AO groups on the same disks

We're not changing the set size. We want to change the Growth increment so that when the CPG increases in size, it always increases by (number of disks/(set size*(set size-1))) for our RAID 5 CPGs and (number of disks/(set size*(set size-2))) for our RAID 6 CPGs. This should mean each time a CPG grows, 1 chunklet from each disk available to the CPG is allocated to the CPG.

eg. RAID5, set size 7 (7 shelves), 42 disks. This should result in a growth increment of 36GB. If we don't tune our volumes between CPGs, we run the risk that the chunklets in use for a single volume might not be evenly balanced across all disks.

Author:  MammaGutt [ Fri Feb 09, 2018 9:38 am ]
Post subject:  Re: Multipe AO groups on the same disks

Same should apply. Change your CPG and tune. Tunesys should tune everything that is in the CPG but not according to the rules.

Author:  bbarbaros [ Fri Feb 09, 2018 10:58 am ]
Post subject:  Re: Multipe AO groups on the same disks

Last tunesys I did took 2.5 months :shock: :shock: :shock:

Author:  MammaGutt [ Fri Feb 09, 2018 12:26 pm ]
Post subject:  Re: Multipe AO groups on the same disks

If you have a lot of NL capacity or a lot of big 10k drives I believe you. I usually put max threads and try to avoid NL... Those drives are slow and huge. Having to rewrite everything there takes weeks.

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