Restoring a folder from a snapshot?

You can revert an entire snapshot by starting the SnapRevert job but that doesn't sound like what you want to do.  You could try running the copy on the cluster itself and the network traffic.

If the home directory has a ton of files, it will take a long time regardless of where you do it.  But running it on the cluster could eliminate some of the work in the process.

I believe that there is way using DomainMark with SnapRevert but I haven't had a chance to test it yet.

I'll include what my SE sent me and you can experiment.  I haven't validated this AT ALL.

Keep in mind that this wipes out everything in that directory. The whole domain mark part is what allows us to make the folder ReadOnly during the duration of the restore process.  It makes it a bit more confusing than necessary.

kcisilon1-1# isi snapshot list

ID   Name Path

---------------------------------------------------------

2    testing123 /ifs/Share01

4    Snapshot: 2014Nov21, 11:10:25 AM /ifs/Share01

6    ScheduleName_duration_2014-11-21-_11-15 /ifs/data

7    testingabc /ifs/data

---------------------------------------------------------

kcisilon1-1# isi job start DomainMark --root=/ifs/Share01 --dm-type SnapRevert

Started job [134]

kcisilon1-1# isi job start SnapRevert --snapid 2

Started job [135]

I can run a quick test in my lab.  I could be wrong on this, but that's just how I've always understood it.

But it's simple enough to test

Right, but that will do the entire snapshot, not a subdirectory of the snap.  That is the key difference.

Is there no way to restore just a piece of the snap?  Isn't that what DomainMark is for?

If we can't restore it, it really pushes customers to snapshot at lower levels which is not what we really want.

, it was good to chat with you last Tuesday (NFSv4 conversation)

Honestly i did not know about SnapRevert, is it an incremental restore or it will overwrite everything in the original location ?

Adam…

The domainmark must be done at the same path that the snap is taken at.  Think of it this way, on a VNX its really easy to define what data you’re protecting with a checkpoint, right?  A single UXFS filesystem with a max size of 16TB.  How can you restore a VNX snap?  The whole thing or manually copy the data back, period.  Snaprevert works the same way, but for snaprevert to work, it has to understand the boundaries of the data the snap encompases. That's where the domainmark comes into play.  You run the domainmark so that the cluster understands those boundaries.  SyncIQ has an identical concept that's part of the resync-prep job.  The domainmark only has to be run once.  Protection Domains are used really for four things:

1. SyncIQ

2. SnapshotIQ

3. SmartQuotas

4. SmartLock

Want to view the domains on your cluster? Run isi domain list, or isi_classic domain list (depending on your version of OneFS)

Hope this helps,

Chris Klosterman

Senior Solution Architect

EMC Isilon Offer and Enablement Team

Email: chris.klosterman@emc.com

Twitter: @croaking

Good to talk to you too.  I thought that was you.

But SnapRevert should wipe out everything and make it exactly like the snapshot.  If you want to do an incremental restore, you can do that via some form of copy with the proper flags to not over-write a new file, etc. 

So far, my lab is confirming what I thought.  When I do the DomainMark on the root of the snap, the SnapRevert works.  If I do the DomainMark on a subdirectory, the SnapRevert fails.

I'd love to be wrong on this, but so far it doesn't appear to be so.  If I get any new info, I'll pass it along and, certainly, if anyone else can make this work, please post it here.

I'm still playing with it because it's bugging me.  I'm not finding much use for the DataMark step but everything I read says you should do it.  The SnapRevert job takes a snapID as an argument and that seems to handle that piece well.

I'll check with the brain trust as well.  This kind of crap bugs me when I think I understand something and then I realize I don't know it as well as I thought I did.

so there is no reason to use DomainMark, SnapRevert is sufficient to roll back to specific snapshot ? (how do you specify what snapshot you want to roll back to ? )

Interesting, but doesn't the snapid define the root of the snap anyway, so if I tell it to revert to snapid=123, shouldn't it be clear that I want to restore the path of that snap, since it's all or nothing anyway?

Nevertheless, SnapRevert doesn't work without prior DomainMark. Think of two kinds

of snapshots, normal (old) ones and "revertible" ones.

"works great" is relative.  If the dataset is large, this can be a very lengthy operation - perhaps days - since it's actually doing a copy of the files.  Ideally, we should be able to revert the data from a subset of the snapshot by just manipulating metadata pointers.  I had to revert a 35TB accidental deletion the other data.  It wasn't pretty.  And to make matters worse, that data is now treated as new so it starts snapshotting that data while still having the old snapshots lying around until they expire. And put SyncIQ on top of that data and the problem intensifies.

SnapRevert is too simplistic for me in its current state.  If I have 100 projects under /ifs/project, and I'm snapshotting at /ifs/project, I can't revert the data for just one project without wiping out the other 99.