HPE EVA Storage

Which one is faster : restore from a snapshot or from a mirrorclone ?

 
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Eric SAUBIGNAC
Honored Contributor

Which one is faster : restore from a snapshot or from a mirrorclone ?

Bonjour @tous

Everything is in the question but I will detail a little bit more ...

I am helping a client to build a plan to recover if necessary from saved data after a migration process (around 1.3 TB). Storage Array are EVA 6000.

I have currently no background in restoring a vDisk from its mirrorclone and I wonder if it as fast as a restoration from a snapshot which in fact just moves some data pointers. Does a restore from a mirroclone copy back the datas or does it just reassemble datas pointers ?

Thanks in advance

Eric
5 REPLIES 5
Eric SAUBIGNAC
Honored Contributor

Re: Which one is faster : restore from a snapshot or from a mirrorclone ?

/(bb|[^b]{2})/ ... that is the question
TTr
Honored Contributor
Solution

Re: Which one is faster : restore from a snapshot or from a mirrorclone ?

http://h18000.www1.hp.com/products/quickspecs/11616_div/11616_div.html

You probably have seen this already.
You could mount the mirrorclone LUN in place of the original Vdisk and be done with. If you must have the original vdisk, based on the description in the URL, restoration is instant. I don't see how that can happen since the entire mirrorclone must be copied completely back to the vdisk. I can only assume that the syncing starts with pointers (just like a snapshot) but in the background the full block-based copying is taking place.
I don't have any EVA experience, maybe somebody else will reply with more info.
jagman
New Member

Re: Which one is faster : restore from a snapshot or from a mirrorclone ?

If the data on the mirror clone is fine then just mount the Mirror clone. It is an exact replica of the original disk up to the point when it was detached from the MASTER ( original disk). There is no restore since it is ready to go!

John
Eric SAUBIGNAC
Honored Contributor

Re: Which one is faster : restore from a snapshot or from a mirrorclone ?

Thanks for your answers.

@all :

In fact an other objective of the recover plan is to have very few action to realize if a rollback should occur.

And we are in an HP-UX 11iv3 environment. So presenting the clones in place of the original disks would have a significant impact since it is not transparent to the OS(WWN change)

So you could answer to this "in this case, just use snapshots instead of mirrorclones". Yes, but snapshots could have some significant impacts on EVA performances during the migration process ...

@TTr :

I am a bit leazy in this moment. Not so much time to RTFM ;-) No more to do some tests.

But I guess the link you have pointed answers my question. Here is an extract :

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MirrorClone will track all changed blocks and can re-sync with the source LUN to create a new point-in-time copy, or can be used to instantly restore the source
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Note the "instantly restore the source".

Though I have not so much time, I will do a little test at noon instead of having lunch ... :-( and post the results
Eric SAUBIGNAC
Honored Contributor

Re: Which one is faster : restore from a snapshot or from a mirrorclone ?

Test done.

Restore of a mirrorclone is effectively instantly and saved datas can be reached immediately.

But because EVA will keep both the source vDisk and the mirrorclone after a restore, datas are synchronized again in the back ground. So we have a slight overhead at EVA level. It tooks about 30 mns to achieve the job (400 GB)

But as said Lavoisier, "Nothing is lost, nothing is created. Everything is transformed". It is always a true law in IT !

TTr get the point.

Thanks to every one

Eric