How to predict the snapmirror transfer size

Many of us wanted to know what is the file size we would be transfering while we intitate a snapmirror. I have made an real time example here hope it helps

Vol1 is the volume we use for transferring( I have kept the same name at both destination and source for eazy understanding)

sourcefiler> snap list vol1
Volume vol1
working...

  %/used       %/total  date          name
----------  ----------  ------------  --------
  2% ( 2%)    1% ( 1%)  Oct 23 04:15  destinationfiler(0123456789)_vol1.745 (snapmirror)
  5% ( 4%)    2% ( 1%)  Oct 22 23:01  hourly.0
  9% ( 4%)    3% ( 1%)  Oct 21 23:01  hourly.1
 12% ( 4%)    4% ( 1%)  Oct 20 23:01  hourly.2
 18% ( 7%)    6% ( 2%)  Oct 19 23:04  hourly.3
 21% ( 5%)    7% ( 1%)  Oct 18 23:01  hourly.4
 25% ( 6%)    9% ( 2%)  Oct 17 23:02  hourly.5
 28% ( 5%)   11% ( 1%)  Oct 16 23:01  hourly.6

In the above we check snap list currently for the volume at the source ( it will list the base snap shot for the source)

destinationfiler*> snap list vol1
Volume vol1
working...

  %/used       %/total  date          name
----------  ----------  ------------  --------
  0% ( 0%)    0% ( 0%)  Oct 23 04:15  destinationfiler(0123456789)_vol1.745
  4% ( 4%)    1% ( 1%)  Oct 22 23:01  hourly.0
  8% ( 4%)    2% ( 1%)  Oct 22 04:15  destinationfiler(0123456789)_vol1.744
  8% ( 1%)    2% ( 0%)  Oct 21 23:01  hourly.1
 11% ( 4%)    3% ( 1%)  Oct 20 23:01  hourly.2
 17% ( 7%)    6% ( 2%)  Oct 19 23:04  hourly.3
 20% ( 5%)    7% ( 1%)  Oct 18 23:01  hourly.4
 25% ( 6%)    9% ( 2%)  Oct 17 23:02  hourly.5
 27% ( 5%)   10% ( 1%)  Oct 16 23:01  hourly.6


Here we check the snapshot which was used last for the snapmirror.

sourcefiler*> snapmirror destinations -s
Path       Snapshot                       Destination

vol1 destinationfiler(0123456789)_vol1.745 destinationfiler:vol1 ( this command tells which was the snapshot used for the snapmirror) in this case its 745

Iam starting a snapmirror update now

destinationfiler*> snapmirror update vol1
Transfer started.
Monitor progress with 'snapmirror status' or the snapmirror log. ( we started a snapmirror update for vol1)


sourcefiler*> snap list vol1   ( once the snapmirror is intiated we see a new snapshot is created which is 746 in our case)
Volume vol1
working...

  %/used       %/total  date          name
----------  ----------  ------------  --------
  0% ( 0%)    0% ( 0%)  Oct 23 16:46  destinationfiler(0123456789)_vol1.746 (busy,snapmirror)
  2% ( 2%)    1% ( 1%)  Oct 23 04:15  destinationfiler(0123456789)_vol1.745 (busy,snapmirror)
  5% ( 4%)    2% ( 1%)  Oct 22 23:01  hourly.0
  9% ( 4%)    3% ( 1%)  Oct 21 23:01  hourly.1
 12% ( 4%)    4% ( 1%)  Oct 20 23:01  hourly.2
 18% ( 7%)    6% ( 2%)  Oct 19 23:04  hourly.3
 21% ( 5%)    7% ( 1%)  Oct 18 23:01  hourly.4
 25% ( 6%)    9% ( 2%)  Oct 17 23:02  hourly.5
 28% ( 5%)   11% ( 1%)  Oct 16 23:01  hourly.6

destinationfiler*> snap list vol1   ( on the destination side we see that 744 is deleted and currently it reference to 745 only)
Volume vol1
working...

  %/used       %/total  date          name
----------  ----------  ------------  --------
  0% ( 0%)    0% ( 0%)  Oct 23 04:15  destinationfiler(0123456789)_vol1.745
  4% ( 4%)    1% ( 1%)  Oct 22 23:01  hourly.0
  4% ( 1%)    1% ( 0%)  Oct 21 23:01  hourly.1
  7% ( 4%)    2% ( 1%)  Oct 20 23:01  hourly.2
 14% ( 7%)    4% ( 2%)  Oct 19 23:04  hourly.3
 17% ( 5%)    6% ( 1%)  Oct 18 23:01  hourly.4
 22% ( 6%)    8% ( 2%)  Oct 17 23:02  hourly.5
 25% ( 5%)    9% ( 1%)  Oct 16 23:01  hourly.6


 ( we do snap delta to check the difference between the snapshots which are currently used in our case its 745 and 746) which shows as 25268240 KB as below)

sourcefiler*> snap delta -V vol1 destinationfiler(0123456789)_vol1.745 destinationfiler(0123456789)_vol1.746 

Volume vol1
working...

From Snapshot   To                   KB changed  Time         Rate (KB/hour)
--------------- -------------------- ----------- ------------ ---------------
destinationfiler(0123456789)_vol1.745 destinationfiler(0123456789)_vol1.746 25268240       0d 12:31  2016440.503

this 25268240 is the size we would be transferring during this snapmirror update process.

destinationfiler*> snapmirror status
Snapmirror is on.
Source                                         Destination                        State          Lag        Status
sourcefiler-my_vif-103:vol1   destinationfiler:vol1      Snapmirrored   00:46:56   Idle
sourcefiler-my_vif-103:vol1   destinationfiler:vol1      Snapmirrored   12:34:40   Transferring  (9505 MB done)

we can verify after the snapmirror is done by using snapmirror status -l command at the destination.

destinationfiler*> snapmirror status -l vol1
Snapmirror is on.

Source:                 sourcefiler-my_vif-13:vol1
Destination:            destinationfiler:vol1
Status:                 Idle
Progress:               -
State:                  Snapmirrored
Lag:                    00:08:53
Mirror Timestamp:       Tue Oct 23 16:46:55 IST 2012
Base Snapshot:          destinationfiler(0123456789)_vol1.746
Current Transfer Type:  -
Current Transfer Error: -
Contents:               Replica
Last Transfer Type:     Update
Last Transfer Size:     25268248 KB ( this is one we got using snapdelta command as described earlier( there is 8kb difference than the one which we got earlier im not too sure why this differnce may be someone can point me))
Last Transfer Duration: 00:07:49
Last Transfer From:     sourcefiler-my_vif-13:vol1

Your comments welcome