Simultaneous-write operations during storage pool migration

[smetter]

Hi All,

I came across this link today:

http://publib.boulder.ibm.com/infoc...m.ic.doc/r_techchg_srv_simulwritemig_620.html

It is stated here that in TSM server 6.2,
it is possible to perform a simultaneous migration + stgpool backup for data-migration processes:

The simultaneous-write function during migration can reduce the amount of time required to back up storage pools or copy active data. Data that is simultaneously written to copy storage pools or active-data pools during migration is not copied again to the copy storage pools or active-data pools. For example, suppose that you migrate all the data in your primary random-access disk storage pool nightly and then back up your primary storage pools. By using the simultaneous-write function during migration, you can significantly reduce the amount of time required for backup operations.

With Tivoli Storage Manager V6.2, you can specify the simultaneous-write function for a primary storage pool if it is the target for any of the eligible operations (client store sessions, server import processes, and server data-migration processes).

I thought this was only true for
client backup operations -> writing data simultaneously to a DISKPOOL and a COPY POOL.
But NOT for server data-migration processes,
I thought this was a feature that was planned for the future but was not yet available.

I have run some tests however and simultaneous disk pool migration + stgpool backup to copy stgpool did not work in my test environment.

I have tested this by specifying the COPYSTGPOOL parameter on the DISKPOOL to point to the COPY STGPOOL. (I did this modification right before performing the migration,
so it is not possible that the data in the diskpool was already simultaneously
written to the COPYSTGPOOL by the client during backup)

When performing a "migrate stg DISKPOOL lowmig=0",
the data was written only to the primary tape pool, not to the copy stg pool.
(I've verified this by issuing a q mount and checking the volumes mounted and the
tape stgpools they belong too).

Did I do something wrong / did I forget something to set up this functionality
properly?
Can anybody confirm if this functionality really exists or not?

 

[ChrisRees]

Hi

Did you set the AUTOCOPY parameter on the diskpool ?


Cheers



AUTOCopy Specifies when Tivoli® Storage Manager writes data simultaneously to copy storage pools and active-data pools. This parameter affects the following operations:

• Client store sessions
• Server import processes
• Server data-migration processes

If an error occurs while data is being simultaneously written to a copy storage pool or active-data pool during a migration process, the server stops writing to the failing storage pools for the remainder of the process. However, the server continues to store files into the primary storage pool and any remaining copy storage pools or active-data pools. These pools remain active for the duration of the migration process. Copy storage pools are specified using the COPYSTGPOOLS parameter. Active-data pools are specified using the ACTIVEDATAPOOLS parameter.
Possible values are: None Specifies that the simultaneous-write function is disabled.CLient Specifies that data is written simultaneously to copy storage pools and active-data pools during client store sessions or server import processes. During server import processes, data is written simultaneously to only copy storage pools. Data is not written to active-data pools during server import processes.MIGRation Specifies that data is written simultaneously to copy storage pools and active-data pools only during migration to this storage pool. During server data-migration processes, data is written simultaneously to copy storage pools and active-data pools only if the data does not exist in those pools.All Specifies that data is written simultaneously to copy storage pools and active-data pools during client store sessions, server import processes, or server data-migration processes. Specifying this value ensures that data is written simultaneously whenever this pool is a target for any of the eligible operations.

 

[smetter]

Thanks for the reply,
Figured this one out.

I had to set AUTOCOPY=MIGRATION indeed,
but not on the DISKPOOL, but on the primary tape pool.

Apparently you have to set the COPYSTGPOOLS, AUTOCOPY and COPYCONTINUE parameters on the stgpool that is used as DESTINATION for the migration operation for simultaneous write to work at migrate stg process level.

<=> simultaneous write at client backup level, where you have to set these parameters on the diskpool.