What is the proper reversal action during a cascaded Snapmirror

ROBIN_YAN_WFHK — Thu, 05 Jun 2025 05:39:30 GMT

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

resqme914 — Thu, 27 Mar 2014 14:38:28 GMT

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.

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What is the proper reversal action during a cascaded Snapmirror

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