Jack,

Before I bought my new libraries last year, I did exactly that.

The only wrinkles I saw were:
1) TSM can handle files larger than a tape volume by spanning volumes;
reclaiming such a file to a disk pool  that holds "a tape" does not work
but you won't know until AFTER the system tries to write the capacity of
the disk pool and then rolls back that transaction;
2) Reclamation takes twice as long because the data travels via two
processes - tape to disk, followed by disk to tape.

This is also a viable option if you have more than one drive but don't have
enough to avoid drive contention.  I used it for a very busy two drive
library.

Tab Trepagnier
TSM Administrator
Laitram Corporation







                    "Coats, Jack"
                    <Jack.Coats@BANKSTE       To:     ADSM-L AT VM.MARIST DOT 
EDU
                    RLING.COM>                cc:
                    Sent by: "ADSM:           Subject:     Re: tape become full 
in 21 percent.
                    Dist Stor Manager"
                    <[email protected]
                    DU>


                    11/25/2002 11:44 AM
                    Please respond to
                    "ADSM: Dist Stor
                    Manager"






To do a reclamation on a single drive system you need some disk space.
I would suggest a tapes worth of space, but it can deal with less.

Define a disk file as a sequential access storage pool (call it SEQDISK).
The migration pool for the SEQDISK would go to would be TAPEPOOL
(assuming that is your tape pool).  Set TAPEPOOLs recovery pool to be
SEQDISK.  Now start a recovery.  It will read the tape(s) to disk, then
write to TAPEPOOL output tape as necessary.  Rinse. Repeat.

As always, YMMV, and don't try this at home without a net.
At least that is my current understanding.  Other opinions are welcome.
Someone want to shoot holes in it for me?
> -----Original Message-----
> From: Zlatko Krastev [SMTP:acit AT ATTGLOBAL DOT NET]
> Sent: Monday, November 25, 2002 8:32 AM
> To:   ADSM-L AT VM.MARIST DOT EDU
> Subject:      Re: tape become full in 21 percent.
>
> Consider following scenario:
> 1. you backup say 40 GB
> 2. next day you backup 40 GB of which 35 GB updated - 35 GB from step 1
> expire.
> 3. perform step 2 for four days.
>
> The result you have 40 + 4x 40 GB = 200 GB written on tape. Tape reached
> the end and becomes "Full". At the same time you had 4x 35 GB = 140 GB
> expired. Thus you tape holds 200 - 140 = 60 GB (30%) real-data. The rest
> is gaps. Reclamation precess (which is hard, close to impossible, to do
on
> single drive) can help.
>
> Zlatko Krastev
> IT Consultant
>
>
>
>
>
>
> Sudheer Kumar <sudheer AT COSMOS.DCMDS.CO DOT IN>
> Sent by: "ADSM: Dist Stor Manager" <ADSM-L AT VM.MARIST DOT EDU>
> 26.11.2002 14:22
> Please respond to "ADSM: Dist Stor Manager"
>
>
>         To:     ADSM-L AT VM.MARIST DOT EDU
>         cc:
>         Subject:        tape become full in 21 percent.
>
>
> Hi
>
> I am using LTO 3580 tape drive. but my tape capacity is 100/200GB but
> never got more than 31% utilization. When it reaches 25 to 31percent it
> become Full.Can anybody tell me what could be the reason.
>
> Regards
>
> Sudhir