[Gluster-devel] Appending time to snap name in USS

[Poornima Gurusiddaiah]

Hi, 

Windows has a feature called shadow copy. This is widely used by all 
windows users to view the previous versions of a file. 
For shadow copy to work with glusterfs backend, the problem was that 
the clients expect snapshots to contain some format 
of time in their name. 

After evaluating the possible ways(asking the user to create 
snapshot with some format of time in it and have rename snapshot 
for existing snapshots) the following method seemed simpler. 

If the USS is enabled, then the creation time of the snapshot is 
appended to the snapname and is listed in the .snaps directory. 
The actual name of the snapshot is left unmodified. i.e. the snapshot 
list/info/restore etc. commands work with the original snapname. 
The patch for the same can be found @ http://review.gluster.org/#/c/9371/ 

The impact is that, the users would see the snapnames to be different in the ".snaps" folder 
than what they have created. Also the current patch does not take care of the scenario where 
the snapname already has time in its name. 

Eg: 
Without this patch: 
drwxr-xr-x 4 root root 110 Dec 26 04:14 snap1 
drwxr-xr-x 4 root root 110 Dec 26 04:14 snap2 

With this patch 
drwxr-xr-x 4 root root 110 Dec 26 04:14 snap1 at GMT-2014.12.30-05.07.50 
drwxr-xr-x 4 root root 110 Dec 26 04:14 snap2 at GMT-2014.12.30-23.49.02 

Please let me know if you have any suggestions or concerns on the same. 

Thanks, 
Poornima 
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