Re: ADSM directly to tape

1997-12-18 11:59:44
Subject: Re: ADSM directly to tape
From: "Kelly J. Lipp" <lipp AT STORSOL DOT COM>
Date: Thu, 18 Dec 1997 09:59:44 -0700

The simplest way to send data directly to tape is to create a tape storage
pool and then define a backup copy group within a management class, call it
direct_to_tape, and point the destination storage pool at the tape storage
pool you defined.  Then make sure that the direct_to_tape management class
is the default management class in that policy set, or use the include list
in the client options file to send the data to that management class.

The downside is only one client can write to one tape at a time. If you
have multiple tape drives in a robot and the devclass mountlimit parameter
is greater than one, you can have more than one backup to tape at a time.
 Mountlimit can't be greater than the number of tape drives you have,

An alternative would be to have a disk storage pool in front of the tape
storage pool.  Point the direct_to_tape backup copy group to the disk
storage pool instead.  Set the migration threshold of the disk storage pool
to zero.  With this approach, you can have as many simultaneous backups as
you want; the data will be "buffered" in the disk storage pool but
immediately migrated to tape.  You can read one of my diatribes from
yesterday to understand how migration works.  To use more than one tape
drive during this migration, set the migration process parameter to the
number of tapes you want to use.  Consider one less than the number of
drives you have in your robot.  That way if a higher priority activity like
a database backup needs to happen, your migration will continue.  Doing
this will also allow a restore a to occur during a backup.  Don't forget
the mount limit parameter in the device class.

I hope this helps.  If it doesn't let me know.


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