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What is the proper reversal action during a cascaded Snapmirror

Here's a quick question about snapmirror in the cascade.

If there is a cascaded Snapmirror replication A->B->C and a reverse will happen between A & B, Do I need to quiesce/break the replication between B & C in advance or I can just leave it? Please also mention the reason.

Thanks!

Robin

Re: What is the proper reversal action during a cascaded Snapmirror

Not a hundred percent sure as to what you're really trying to accomplish, but the simple answer is no you do not have to quiesce/break the replication between B and C prior to reversing A and B because you're not really affecting the relationship from B to C.  In effect, you're turning B into the "source" for both A and C.

For example... this is "B" before the reversal (1netapp03 -> 1bon01 -> 5netapp01)...

san-1bon01> snapmirror status

Snapmirror is on.

Source                  Destination             State          Lag        Status

SAN-1NETAPP03:test_vol  san-1bon01:test_vol     Snapmirrored   00:11:31   Idle

san-1bon01:test_vol     San-5netapp01:test_vol  Source         00:11:31   Idle

After I quiesce and break the A->B relationship, then "reverse resync" B->A (without doing anything to B->C relationship)...

san-1bon01> snapmirror status

Snapmirror is on.

Source                  Destination             State          Lag        Status

SAN-1NETAPP03:test_vol  san-1bon01:test_vol     Broken-off     00:21:23   Idle

san-1bon01:test_vol     SAN-1NETAPP03:test_vol  Source         00:05:20   Idle

san-1bon01:test_vol     San-5netapp01:test_vol  Source         00:21:23   Idle

san-1bon01>

As you can see, B is now "source" to A and C.

To go back to normal, you update/quiesce/break the B->A relationship then resync the A->B relationship...

san-1bon01> snapmirror status

Snapmirror is on.

Source                  Destination             State          Lag        Status

SAN-1NETAPP03:test_vol  san-1bon01:test_vol     Snapmirrored   00:00:14   Idle

san-1bon01:test_vol     SAN-1NETAPP03:test_vol  Source         00:11:21   Idle

san-1bon01:test_vol     San-5netapp01:test_vol  Source         00:27:24   Idle

san-1bon01>

You can then delete the B->A relationship that was created when you reversed and after that you should be back to normal...

san-1bon01> snapmirror status

Snapmirror is on.

Source                  Destination             State          Lag        Status

SAN-1NETAPP03:test_vol  san-1bon01:test_vol     Snapmirrored   00:03:05   Idle

san-1bon01:test_vol     San-5netapp01:test_vol  Source         00:30:15   Idle

san-1bon01>

Hope that helps.