moving PDs to rebalance system

[Noss]

Has anyone gone through the process of having to move PDs in use, from existing drive enclosures, to rebalance a system after adding a new drive enclosure with less drives than the existing drive enclosures?

Is it a simple procedure? What would be the best way of moving data from the existing disks so they can be moved?

[Dennis Handly]

Have you looked at tunesys?  What 3PAR OS version do you have?

[Noss]

Hi Dennis,

Version 3.1.3.

I've looked at tunesys to balance chunklets across new additional drives but not to move all chunklets off an existing physical drive.

Thanks

[rocru_rocru]

So if I understand, you added another tray (enclosure) to your 3PAR system?

Or have you added another 3PAR and robbed PDs from the old and place into the new for better balance?

No matter what, you need to run tunesys (nodes): this will provide even distribution across all PDs.

tunesys wont move 'all' chunklets off existing PDs; it rebalances chunklets across all existing, available PDs.

Run tunsys in Analysis only; output will tell you whats needed.

[Sheldon Smith · Accepted solution]

It is not simple. The best way is to open a ticket with HP Support and get a Customer Service Request set up. HP can help you move PDs without damaging your data.

Note: While I work for HP, all of my comments (whether noted or not), are my own and are not any official representation of the company.
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[Amar_Joshi]

Noss,

While I agree that this is real life scenario when the array runs out the available slots and needs extra disk shleves, one should be able to rebalance the PDs (to have almost same number of drives in each enclosure). This is not a simple process and the only advantage of doing so is to get the high-availability. Performace gained by doing so is very minimal because the way 3PAR make the chunklet (and LDs) layout, each VV is already optimized.

Now, by moving the PDs (by vacating the data and repopulating after putting them in new shlef) the VVs are risking data movement. In my opinion, we in such scenario the drives should be left imbalance.

I am always an advocate of providing enough empty slots at first install to make the future upgrade easy and whenever such diskshlef upgrades are needed, fill them with some extra disks to balance the PDs. And let TUNESYS do it's magic to rebalance the chuklets.

Hope that helps.

[Noss]

Thank you for your suggestions. I am beginning to think that have the system temporary unbalanced is an easier option.