On Tue, Mar 07, 2006 at 06:34:50AM -0800, Wayne Johnson wrote:
> I am using filetapes for backups. I have a 120GB Raid array that
> I back up to another 120GB single drive. Unfortunately, I've
> started getting an error during the nightly backup:
>
> taper: tape daily20 KB 4194272 fm 8 writing file: No space left on device
> taper: retrying devserv:/common.2 on new tape: [writing file: No space
> left on device]
> taper: tape daily21 KB 0 fm 0 [OK]
>
> I assume this is because the new files on this "disk" are larger than
> the filetape volume. I figured 4GB would be plenty for a file volume,
> but someone added a new directory with 9 GB of data. Oops.
Yeah, 9GB is a tight squeeze in a 4GB tape ;)
> What is a good size to use for filetape volumes? Can I change these
> sizes after I've started using them? What would be the best way to
> get out of the situation I'm in?
For a physical tape, when you run out of plastic ribbon,
you are out of space regardless of what the tapetype says.
For vtapes, I think the situation is different. The vtape driver
tries to respect the size value in your tapetype definition. So
you can "run out of space" because you exceed your tapetype def
or because the hard disk file system ran out of space.
Assuming you don't have FS space problems, I think you can just
up your tapetype def and claim a bigger size. Then the question
becomes something like "how many vtapes should/can I have and
how big should I claim them to be".
I've been thinking of analogies for this decision making. I think the
"cellular phone plan" analogy works. Two types of plans, fixed monthly
minutes and loss of unused minutes vs. rollover of unused minutes.
If you have a 100GB space for vtapes and want 20 dumps stored (say four
weeks worth of dumps Mon - Fri), then "obviously" the tapetype size
should be 5GB each. That is the "fixed minutes" plan.
But with this you find you run out of minutes some months (opps, I mean
out of space some dumps) and some months you have minutes left over.
Try the rollover minutes (GB) plan. Increase your apparent monthly
minutes (tapetype size) to a larger number. Then any months (dumps)
that didn't fit before can use the unused minutes (GB) from smaller
months.
Of course, if you talk a lot (dump a lot) for too many months, you
will run out of your rollover minutes (i.e. the total file system).
Only you can find, and maintain, the right balance of maximum dump
size, number of vtapes, and file system size.
--
Jon H. LaBadie jon AT jgcomp DOT com
JG Computing
4455 Province Line Road (609) 252-0159
Princeton, NJ 08540-4322 (609) 683-7220 (fax)
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