Re: Moving IPL volume for an LPAR from on-board SSD's to fibre channel attached LUN on SAN which is in a replication relationship with another LUN in a different SAN - any gotcha's with this approach?

Laurence,

I'm not sure exactly what your question is, but I can say that migrating from internal to external storage is absolutely supported. A full save/restore is a valid path for this migration but is NOT the only path. In most cases it will take much less downtime to simply connected the new volumes at the same time as the existing volumes, and migrate the date using IBM i's disk migration capabilities. An outage is required to move the Load Source only but if done right the load source can be drained to a very small amount such that the migration would require a minimal amount of downtime.

I have done this an untold number of times and it is a supported path.

As to replicating the full system using the SANs this is a solution that is getting more and more common and IBM even sells a toolkit to support this.

- DrFranken

On 10/11/2021 4:26 AM, Laurence Chiu wrote:

Subject doesn't provide the whole context.

Situation is a Power 9 with 3 LPAR's running off SSD's. Because of
insufficient IO adapters one LPAR (a DR LPAR for production) hosts the
disks for the other two.

As in the subject we have two SANs in two data centres, and they are in a
metro mirror relationship replicating updates from production to DR managed
by Copy Services Manager (CSM). The production LPAR is using the SAN, the
DR LPAR is still using the SSD's. It goes without saying all the SANs are
fibre channel connected using switches in each data centre and we have done
the appropriate zoning so that the actual hardware can see the SANs. Not
sure it's important but the SANs are IBM FlashSystem V5030's.

What we want to do is the following:
- backup two of the LPARs to tape
- alter the configuration so that the DR LPAR now IPL's off the LUN on the
SAN so it would be identical to production.
- reconfigure the storage so that a different LPAR owns the SSD's and
shares out the storage to the other and then restore the other two LPARs
to the SSD's. from the tape

So now we will have our production and DR LPARs completely in sync and the
DR LPAR able to be IPL'ed in a DR event and have no data lost. It goes
without saying that when replication is taking place the DR LPAR will be
shutdown since SAN replication does not allow both the SAN replication
software to write to the second SAN while an LPAR is also able to write to
it. These options can be handled easily enough using the CSM GUI.

This seems reasonable to me (and is what we do in our IBM mainframe
environment) but Power systems are a bit different and there might be some
constraints in the hardware that I am not aware of. So I would like to be
forewarned before I propose this to our support vendor who when previously
presented with this thought, did not seem sufficiently technically familiar
with this environment to be able to make an informed comment. And this is
not IBM or Kyndryl whom I would trust to either know or reach out in their
organisation to find out!

Thanks for any insight for those who are familiar with this architecture.