I have a customer that is currently replicating (PBR) to a second system via a FC Partnership in the same datacenter.  We are planning to move this to a secondary location and they don't have FCIP infrastructure in place so we were going to convert to IP based PBR in place.  If we do have to start the replication over then we can at least do it with marginal network latency prior to moving it.

I haven't had to do this in quite a few years since Policy-Based has been a thing, nor have I found anything documenting if this is possible, and what steps would be required. I did attempt to create the IP based Partnership, but quickly got the expected error :

CMMVC8370E The remote cluster partnership was not created because it already exists.

For anyone that has done this, are there any gotchas or a link to a document?  Several years experience with Flashsystem, just haven't done this specifically yet.

Thanks All

If you are currently using replication for DR outside a partition, then you would need to unconfigure the replication between the systems to remove the current FC partnership, then create a new IP partnership and reconfigure, which will perform a full sync.  This is because you can't remove a partnership while it's being used by a replication policy.

However, if you are using DR replication within a partition (requires both systems to be running 8.7.1 or later), then the async replication policy there doesn't actually specify a particular system (by design, to allow for easier movement of partitions between systems, but it also happens to help in your scenario too).   This means you could:

1. Stop the partnership
2. Remove the FC partnership
   1. At this point the systems will each log an error to indicate "The remote DR linked partition is missing", which is what you'd expect
3. Create a new IP partnership
   1. Now you can mark the errors fixed on each system and replication will resume.  The catch-up will be an incremental copy.

If you are considering changing to use partitions, the steps are here in the product documentation here:

https://www.ibm.com/docs/en/sanvolumecontroller/8.7.x_cd?topic=recovery-migrating-replication-disaster-use-partitions

One thing to keep in mind is that storage partitions have a more restrictive set of rules about how they can be used compared to the standard system behaviour, and they require each system to have a single I/O group. For example, within a storage partition, all volumes must be in volume groups, and hosts can only be mapped to volumes in the same storage partition. Only SCSI hosts connected by using Fibre Channel or iSCSI are supported in storage partitions. These rules ensure that storage partitions can be nondisruptively migrated to another system in a FlashSystem grid, or be configured for high availability without conflicting with other resources that exist on either of the systems.  These rules apply even if you aren't currently configured as part of a FlashSystem grid.  For full details, refer to the product documentation.

Hope that helps.

I have a customer that is currently replicating (PBR) to a second system via a FC Partnership in the same datacenter.  We are planning to move this to a secondary location and they don't have FCIP infrastructure in place so we were going to convert to IP based PBR in place.  If we do have to start the replication over then we can at least do it with marginal network latency prior to moving it.

I haven't had to do this in quite a few years since Policy-Based has been a thing, nor have I found anything documenting if this is possible, and what steps would be required. I did attempt to create the IP based Partnership, but quickly got the expected error :

CMMVC8370E The remote cluster partnership was not created because it already exists.

For anyone that has done this, are there any gotchas or a link to a document?  Several years experience with Flashsystem, just haven't done this specifically yet.

Thanks All

If you are currently using replication for DR outside a partition, then you would need to unconfigure the replication between the systems to remove the current FC partnership, then create a new IP partnership and reconfigure, which will perform a full sync.  This is because you can't remove a partnership while it's being used by a replication policy.

However, if you are using DR replication within a partition (requires both systems to be running 8.7.1 or later), then the async replication policy there doesn't actually specify a particular system (by design, to allow for easier movement of partitions between systems, but it also happens to help in your scenario too).   This means you could:

1. Stop the partnership
2. Remove the FC partnership
   1. At this point the systems will each log an error to indicate "The remote DR linked partition is missing", which is what you'd expect
3. Create a new IP partnership
   1. Now you can mark the errors fixed on each system and replication will resume.  The catch-up will be an incremental copy.

If you are considering changing to use partitions, the steps are here in the product documentation here:

https://www.ibm.com/docs/en/sanvolumecontroller/8.7.x_cd?topic=recovery-migrating-replication-disaster-use-partitions

One thing to keep in mind is that storage partitions have a more restrictive set of rules about how they can be used compared to the standard system behaviour, and they require each system to have a single I/O group. For example, within a storage partition, all volumes must be in volume groups, and hosts can only be mapped to volumes in the same storage partition. Only SCSI hosts connected by using Fibre Channel or iSCSI are supported in storage partitions. These rules ensure that storage partitions can be nondisruptively migrated to another system in a FlashSystem grid, or be configured for high availability without conflicting with other resources that exist on either of the systems.  These rules apply even if you aren't currently configured as part of a FlashSystem grid.  For full details, refer to the product documentation.

Hope that helps.

------------------------------
Chris Canto
Software Developer
IBM
Hursley

Original Message:
Sent: Tue April 01, 2025 10:38 PM
From: Shaun Anderson
Subject: Change from FC based Partnership to IP based Partnership.

I have a customer that is currently replicating (PBR) to a second system via a FC Partnership in the same datacenter.  We are planning to move this to a secondary location and they don't have FCIP infrastructure in place so we were going to convert to IP based PBR in place.  If we do have to start the replication over then we can at least do it with marginal network latency prior to moving it.

I haven't had to do this in quite a few years since Policy-Based has been a thing, nor have I found anything documenting if this is possible, and what steps would be required. I did attempt to create the IP based Partnership, but quickly got the expected error :

CMMVC8370E The remote cluster partnership was not created because it already exists.

For anyone that has done this, are there any gotchas or a link to a document?  Several years experience with Flashsystem, just haven't done this specifically yet.

Thanks All

------------------------------
Shaun Anderson
------------------------------

<EDIT>

I see this was answered by Vincent.  Thanks All, I think I've got a plan now.

</EDIT>

"If you are currently using replication for DR outside a partition, then you would need to unconfigure the replication between the systems to remove the current FC partnership, then create a new IP partnership and reconfigure, which will perform a full sync.  This is because you can't remove a partnership while it's being used by a replication policy."

The systems are at 8.6....would it be feasible to upgrade both to 8.7.1 or later and then add a partition specifying the existing policy?  Something like:

mkpartition -name MyNewPartition -replicationpolicy MyExistingPBRPolicy

Then once the partition 'structure' is in place make the FC to IP Partnership change?

------------------------------
Shaun Anderson

Original Message:
Sent: Thu April 03, 2025 05:23 AM
From: Chris Canto
Subject: Change from FC based Partnership to IP based Partnership.

If you are currently using replication for DR outside a partition, then you would need to unconfigure the replication between the systems to remove the current FC partnership, then create a new IP partnership and reconfigure, which will perform a full sync.  This is because you can't remove a partnership while it's being used by a replication policy.

However, if you are using DR replication within a partition (requires both systems to be running 8.7.1 or later), then the async replication policy there doesn't actually specify a particular system (by design, to allow for easier movement of partitions between systems, but it also happens to help in your scenario too).   This means you could:

1. Stop the partnership
2. Remove the FC partnership
   1. At this point the systems will each log an error to indicate "The remote DR linked partition is missing", which is what you'd expect
3. Create a new IP partnership
   1. Now you can mark the errors fixed on each system and replication will resume.  The catch-up will be an incremental copy.

If you are considering changing to use partitions, the steps are here in the product documentation here:

https://www.ibm.com/docs/en/sanvolumecontroller/8.7.x_cd?topic=recovery-migrating-replication-disaster-use-partitions

One thing to keep in mind is that storage partitions have a more restrictive set of rules about how they can be used compared to the standard system behaviour, and they require each system to have a single I/O group. For example, within a storage partition, all volumes must be in volume groups, and hosts can only be mapped to volumes in the same storage partition. Only SCSI hosts connected by using Fibre Channel or iSCSI are supported in storage partitions. These rules ensure that storage partitions can be nondisruptively migrated to another system in a FlashSystem grid, or be configured for high availability without conflicting with other resources that exist on either of the systems.  These rules apply even if you aren't currently configured as part of a FlashSystem grid.  For full details, refer to the product documentation.

Hope that helps.

------------------------------
Chris Canto
Software Developer
IBM
Hursley

Original Message:
Sent: Tue April 01, 2025 10:38 PM
From: Shaun Anderson
Subject: Change from FC based Partnership to IP based Partnership.

I have a customer that is currently replicating (PBR) to a second system via a FC Partnership in the same datacenter.  We are planning to move this to a secondary location and they don't have FCIP infrastructure in place so we were going to convert to IP based PBR in place.  If we do have to start the replication over then we can at least do it with marginal network latency prior to moving it.

I haven't had to do this in quite a few years since Policy-Based has been a thing, nor have I found anything documenting if this is possible, and what steps would be required. I did attempt to create the IP based Partnership, but quickly got the expected error :

CMMVC8370E The remote cluster partnership was not created because it already exists.

For anyone that has done this, are there any gotchas or a link to a document?  Several years experience with Flashsystem, just haven't done this specifically yet.

Thanks All

------------------------------
Shaun Anderson
------------------------------