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CPG Raid change and tuning
https://3parug.com/viewtopic.php?f=18&t=3300
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Author:  Biswaranjan [ Fri Oct 18, 2019 4:00 pm ]
Post subject:  CPG Raid change and tuning

Is it safe to use a CPG where the Raid level is modified ?
The data is tuned to a new cpg. Can it be tuned back to the original cpg which is modified to new Raid ? Will there be any data corruption or inconsistency or any impact ?

Author:  MammaGutt [ Sat Oct 19, 2019 1:21 am ]
Post subject:  Re: CPG Raid change and tuning

No problem.

If you just wanted to change RAID on the CPG you could simply have changed it and run tunesys to change for all existing data.

CPG configuration is used when creating LDs (basically writing new data). If you change a CPG configuration it will be used for all new data while the old continues to have the old config. Even that is not a problem. And tunesys will ensure that all data (new and old) is stored according to current CPG configuration.

Author:  Biswaranjan [ Thu Oct 24, 2019 4:34 pm ]
Post subject:  Re: CPG Raid change and tuning

MammaGutt wrote:
No problem.

If you just wanted to change RAID on the CPG you could simply have changed it and run tunesys to change for all existing data.

CPG configuration is used when creating LDs (basically writing new data). If you change a CPG configuration it will be used for all new data while the old continues to have the old config. Even that is not a problem. And tunesys will ensure that all data (new and old) is stored according to current CPG configuration.

Author:  Richard Siemers [ Sun Oct 27, 2019 5:49 pm ]
Post subject:  Re: CPG Raid change and tuning

CPG is a policy that defines how new logical disks are created. When you edit the CPG, the existing data will remain at the old settings, and data written to new LDs will take the new settings. You can run a tunecpg after making a change to convert move the old data into new LDs and remove the old empty LDs.

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