It's really all about comfort level. I have seen people blindly take
backups to DDS-2 or worse drives and never verifying the backups until the
day a backup is needed and then they find out the drive flaked out months or
years ago and no backup is recoverable.
I have seen other people backup to DLTs and verify every backup (and never
finding an error.) The data is so critical they cannot afford any error,
ever.
I should think a proper method would be to verify a backup every week or
every month; just don't go blindly along thinking everything is fine and no
need to check. The verification could even consist of restoring a random
file, usually towards the end of the backup. You could even have a test file
at the end of each backup and just restore that one, every few weeks or
months.
The DDS-3 is a MUCH better device than its predecessors in that technology
and I like it very much.
In answer to your specific question about read after write, DDS drives do
that and if an error is found in the read after write, the drive rewrites
the data automatically.
I offer you the following website for DAT information:
http://www.datmgm.com/
There, among the marketing hype (sigh,) you will find a lot of information
about DAT, past, present and future.
I hope this helps you reach a decision.
Denys
-----Original Message-----
From: HP-3000 Systems Discussion [mailto:[log in to unmask]] On Behalf
Of Dave Powell, MMfab
Sent: Tuesday, October 25, 2005 12:24 PM
To: [log in to unmask]
Subject: Re: [HP3000-L] DDS back online after :STORE
Current versions of 'online' should wait till the drive comes on line, but
older ones (like we have) don't, so a pause after running online is
necessary.
On our site, 30 seconds is not enough (40 seconds works).
Like another poster, I have a command file that can wait for dev 7 to be
ready. Fiddle with its parms and it can wait for any device to have any
status, or just report a device's current status. It's called 'DEVWAIT' and
I posted it back in Feb.
While we are on the subject of vstore after store, the manual for our HP
DDS3 drive (model C15560),under the heading "Getting the most out of....",
says on page 19, "Do not verify (DDS does read-after-write checking
automatically"). Any comments on this from the experts ??
Dave (keeping my verifies in place untill / unless I hear a consensus that
we shouldn't) Powell, MMfab
----- Original Message -----
From: "Jeff Kell" <[log in to unmask]>
To: <[log in to unmask]>
Sent: Tuesday, October 25, 2005 07:33
Subject: [HP3000-L] DDS back online after :STORE
> I'm reasonably certain this has been asked before, and I've tried to
follow
some examples, but I'm at Witt's End. [There is a letter here.]
>
> I've tried to reincarnate our :VSTORE-after-:STORE method of backup and
verify, but with autoreply set on the tape drive now. We've never used
autoreply before (long story) and I'm having trouble with the sequence of
events in the backup job that results in getting a tape request waiting for
a
reply, rather than finding the mounted tape. The guts of the job does this:
>
> > #tellop Backup job is beginning...
> > #devctrl.mpexl.telesup 7 compression=enable eject=disable load=online
> > #back7x24
> > #tellop Backup job is complete.
> > #pause 60
> > #tellop Verifying...
> > online.util.lps 7
> > #pause 30
> > #devctrl.mpexl.telesup 7 compression=enable eject=enable load=online
> > #vstore *backup;@[log in to unmask]@;progress=1
>
> I've tried this, as well as doing the devctrl before the online.util.lps,
various pauses, and can't get a consistent result. More often than not, it
doesn't work, and there is a reply pending in the morning for the vstore.
>
> The version of "online" is:
>
> > ONLINE A0a Copyright (c) 1991 Allegro Consultants, Inc. (408)
252-2330
>
> I tried without online at first, and threw it in there later in hopes it
would help. It did, but still not consistently.
>
> Can anyone share their solution to achieve the desired result?
>
> Jeff
>
> * To join/leave the list, search archives, change list settings, *
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>
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