AW: ADSM & HSM Stub Files

We've tried out Seagate's storage migrator and found it not ready for our
purposes yet. The product definitely is developing into the right direction,
but there are some points where the concepts of storage migrator and ADSM
aren't compatible.

I'll try to give an idea about some of these points:

ADSM holds an "image" of each backed up filespace. To provide both user and
administrator with a transparent system, ADSM shall not back up any
stubfiles but keep the original. Just think of the case of a disaster.
You'll want to buy servers as large as possible and bring back as much data
as possible within a time range as small as possible. So you won't want to
restore stubfiles, will you? 
With storage migrator and ADSM it looks like all this is possible. We tried
it and it looked very good - until I made a small mistake. I saw that the
volume on the NT machine had a "wrong" volume label and I changed it, then I
forgot to do the same change in ADSM (this was before V3PTF5). During the
next backup ADSM tried a new initial fullbackup and recalled all migrated
files... In a production environment we'd have had a nice overflow. 
So, when you switch off the right for ADSM to recall files, you get an
incomplete backup, when you grant ADSM the right you might get a disk full
error when any cartridge fails and ADSM tries to backup some active files
for a second time...

Storage Migrator is very transparent to the user, sometimes too transparent.
When a file has to get recalled, the user doesn't get any information on the
amount of time he has to wait. The user doesn't even know that the file was
migrated and it has to travel back from the hsm system to the server before
access is possible. I'm sure, many of our users will think the system hangs
when a restore isn't finished within 10 seconds and then press the reset
button...
I heard that there exists an application for the workstation that asks the
user before it starts a recall, but imagine you want to copy a directory
containing 1000 migrated files to another location, will you then have to
click on "yes, do the recall" 1000 times?


I hope Seagate Software will continue the development of this tool, that
could make Storage Migrator a powerful alternative to expanding diskspace
indefinitely.

Regards, Michael
--
Michael H. Bartl
Michael H. Bartl
ADAC e.V. (Rechenzentrum, Organisation und Planung)
Tel.: (089) 7676-4063, Fax: (089) 7676-8161
mailto:michael.bartl AT zentrale.adac DOT de
http://www.adac.de