2 Bronze

VLUN Migration and Pinning while under FAST VP control

I've read through the "Best Practices for Nondisruptive Tiering via EMC Symmetrix Virtual LUN Technology" guide and have a couple questions ...

Firstly ...

That document states the following:

 

"In the case where a thin device has allocations across multiple pools, as the result of FAST VP related activity, VLUN VP can be used to consolidate all allocated extents back to a single thin pool. This thin pool can be that which the thin device is currently bound to, or can be a separate thin pool."

Does this mean that ALLextents associated with a VLUN WILL BE moved to the target pool even if FAST VP has previously relocated them?

Scenario:

I have a SATA pool and and EFD pool. A TDEV is bound to the SATA pool and under FAST VP control. FAST VP has relocated extents to the EFD pool. I introduce a FC pool and want to rebind/migrate the TDEV from the SATA pool to the FC pool. Do the extents that FAST VP moved to the EFD pool get migrated/moved to the FC pool along with those from the SATA pool?

Secondly ...

What happens when you pin a device that FAST VP has already moved some extents? Do those moved extents get pinned to whatever pool they're currently in? Do they get moved back to the binding pool and get pinned there?

4 Replies
3 Argentum

Re: VLUN Migration and Pinning while under FAST VP control

Hi,

Pinning will lock all current extent allocations for the device in their current locations, and will prevent FAST VP from relocating them.

So they will be pinned to whatever pool they are currently in..

Regards

Amita Wasson

4 Tellurium

Re: VLUN Migration and Pinning while under FAST VP control

Ques 1: "Do the extents that FAST VP moved to the EFD pool get migrated/moved to the FC pool along with those from the SATA pool?"

It totally depends on the policy you have set and if your data needs to be demoted to FC pool? and If data does not qualify to be in FC then your extents will remain in EFD. You can force it though by giving a high weightage to FC pool.

Ques 2: Does this mean that ALLextents associated with a VLUN WILL BE moved to the target pool even if FAST VP has previously relocated them?

Yes, thats what Virtual LUN migration does.

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2 Bronze

Re: VLUN Migration and Pinning while under FAST VP control

I introduce a FC pool and want to rebind/migrate the TDEV from the SATA pool to the FC pool. Do the extents that FAST VP moved to the EFD pool get migrated/moved to the FC pool along with those from the SATA pool?

Here's my take on it.  Someone please correct me if im wrong on this.

Note the distinction between rebind / migrate in your sentence above.  When you rebind a TDEV from SATA pool to FC pool only newly allocated extents aka new data  will land in the FC pool.  Rebinding does not migrate extents already allocated to SATA and EFD as a result of FAST VP shaking things up.  You must first migrate with VLUN VP  to FC pool to consolidate.

2 Bronze

Re: VLUN Migration and Pinning while under FAST VP control

You take is accurate (as I've done this many times). Also note, rebinding changes the subscription of the whole tdev to the newly bound pool, but doesn't change the allocation (that's tripped some people up).

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