--> ... doesn't work in a trigger ...

It can be made to work within single script. After lowering the thresholds
you may loop waiting the migration process to start and return the old
values.
But you have to take a note: returning the old values will end the
migration after transaction completion. Example:
1. Diskpool is 77% full.
2. highmig,lowmig=0 and migration starts.
3. Highmig=90 lowmig=75
4. Migration transaction moves some data and diskpool usage is lowered to
74%.
5. Before starting new transaction the lowmig threshold is compared and
migration ends (with success).

Usually migration is started by lowering only highmig threshold. Verify
appropriate high and low migration thresholds are set. Maybe you need to
have lowmig=0 and update highmig=0 followed by highmig=90.

--> ... if in this moment a client makes a backup, it'll write to the tape ...

Incorrect. The actual sequence is:
0. The diskpool is empty
1. The client starts backup and files go to *diskpool*!
2. immediately after first (!) client transaction is completed, migration
process starts
3. Migration is moving diskpool data to tape and client is writing to the
diskpool.

You can easily verify this by issuing `q pr` and `q se f=d`. If you
statement was true, the mount must be listed as owned by the session
(direct-to-tape). In fact the volume is mounted by the migration process
and shows up in `q pr` output!
Client writes to disk as you prefer :-)
It is possible that migration to tape is faster than the client sending
the data. In such cases (if highmig=0) migration finishes before next
client transaction can complete and diskpool usage during client backup is
always nearly 0%. You can verify this behavior finding *many* migration
processes starting and ending successfully during client backup.

Zlatko Krastev
IT Consultant






tani <tani AT MAIL2.UDC DOT ES>
Sent by: "ADSM: Dist Stor Manager" <ADSM-L AT VM.MARIST DOT EDU>
05.08.2003 12:05
Please respond to "ADSM: Dist Stor Manager"


        To:     ADSM-L AT VM.MARIST DOT EDU
        cc:
        Subject:        Migrate to tape


 Hi,

 Is it posible to migrate data from disk to tape whitout modify the high
and
low parameters  of the storage pool?

 upd stg diskpool hig=0 low=0
 upd stg diskpool hig=90 low=75

 This method doesn't work in a trigger because it's necessary a short
interval
 of time between the first and second command to start the migration.

 I must use two tiggers to be able to perform the migration.

 Other problem, it's while the parameters in the storage pool are fixed to
zero and if in this moment a client makes a backup, it'll write to the
tape,
not to disk array.
 Are there any solution to this problem? I'ld prefer the clients write the
data to disk array, always.


 Thanks in advance