"ADSM: Dist Stor Manager" <ADSM-L AT vm.marist DOT edu> wrote on 05/10/2011
04:59:03 AM:

>> From: ronnor <tsm-forum AT BACKUPCENTRAL DOT COM>
>> To: ADSM-L AT vm.marist DOT edu
>> Date: 05/10/2011 11:30 AM
>> Subject: Flashcopy manager
>> Sent by: "ADSM: Dist Stor Manager" <ADSM-L AT vm.marist DOT edu>
>>
>> Hi,
>>
>> I am currently working with Tivoli Flashcopy manager to create
>> snapshots for application data (Exchange & SQL data in my case). I
>> am using San volume controller to save my snapshots on space
>> efficient volumes. I followed a guide for configuring all of this,
>> but there is still one thing I do not understand.
>>
>> So here's my current configuration: I have created 2 source volumes
>> and mapped them to my SQL server. Then i created 2 target volumes,
>> mapped them to my VSS_FREE host. But then they say in the guide
>> that during backups, these target volumes move to the VSS_RESERVED
>> host. I don't understand why this happens.

This is done under the covers by the IBM Hardware VSS Provider for SVC.
It does this so those LUNS are not utilized by VSS operations from other
machines performing VSS snapshots. For persistent snapshots,
(BACKUPDESTINATION=LOCAL), the VSS snapshot LUNS will assigned to the
machine that performed the snapshot until the backup expires.


>> And also, are the target
>> volumes exact copies of the source volumes? I found this a little
>> bit vague in the guides.

Logically, they are exact copies. Physically, there are two types:
1. THIN-PROVISIONED, which only contain the changed blocks
2. FULL COPIES, which contain a duplicate copy of the LUN


>>
>> Also, can snapshots be made on the same volumes, or do new volumes
>> get created? For example if you make 3 snapshots, are there 3
>> volumes created for this?

You need to have a separate LUN provisioned in your VSS_FREE pool
for each snapshot you make.

Here is a link to a whitepaper that might help you:
   http://w3-03.ibm.com/support/techdocs/atsmastr.nsf/WebIndex/WP101639