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need explanation of application snapshot

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pob579
Advisor

need explanation of application snapshot

Hello,

 

please explain application snapshot feature. Practical use and advantages.

I used  a lot snapshot (checkpoints) in hyper-v  for having the ability to come back to previous OS state.

 

Does application snapshot relates to backup? How we use it in P4000 environment?

 

Thx.

3 REPLIES
HenryLee
Occasional Visitor
Solution

Re: need explanation of application snapshot

We just installed this same unit and I'm currently working to understand the snapshots myself. I'm a SQL Server DBA so take my comments in that context.

 

The application managed snapshot quiesces the application, the point in time does not. Quiesce is a fancy word for pausing writes so you get a consistent view of the data.

 

The snapshots are super fast, like instant, because they are just pointers back to the original data. Subsequent snapshots track any changes. Because these snapshots are simply pointers (and not a compete copy of the data), they are depenent on the original data being available. So this can protect you against logical problems (in my case, someone drops a table), however, they don't help if anything happens to the original volume or LUN. So you still need to backup to a secondary location.

 

Again, this is my understanding after only a month or so with the unit. Please take with a grain of salt.

Re: need explanation of application snapshot

Almost a 100% ;) Yes - the P4000 supports VSS aware snaps, as well as ESX snaps in SAN/iQ 9.5. So, yes the application aware snap is not only a point in time but applicaiton consistent.

The original volume will always be protected because all new writes (which are the only things that can corrupt a volume) go to new blocks. When the next snap occurs, that is just another layer ontop of the old lun - therefore you can mount different points in time.
pob579
Advisor

Re: need explanation of application snapshot

Thanks!

Robert, I marked Henry's answer as a solution. Anyway you confirm that his answer is Almost 100% accurate.

:)