1. Slightly less time than it takes to backup 32760/3339 (approx. 9.81)
mod 3 volumes that are being stacked to the same output tape. Figure
some housekeeping occurs when the backup software finishes one volume &
then starts another. The difference should be minuscule when total
number of unused tracks is held constant.
2. Modern tapes can hold multiple volumes, large or small. They also
record in a serpentine fashion, back & forth, so high speed positioning
to a given location is quicker.
3. From a dataset level backup, which is what should be used for this
purpose, cylinder location is irrelevant. Competent restore software
should be able to restore a single dataset even from a full volume
backup. If the actual software in use cannot do this, and you don't
have a dataset level backup available, then yes, restoring an entire
large volume for a single dataset will take longer. Note that the
sooner the accidental modification is detected, the more likely it is
that the changed data has not even been backed up yet, the likelier the
latest dataset backup is valid. Simple, quick restore. For deleted
datasets, the recovery could be done months later, depending on your
deleted dataset backup retention policy.
Skip Robinson wrote:
The idea of massive volumes is intriguing, but my concern would be
backup/restore. On some our non-z platforms we have huge volumes many times
the size of 3390-3. When one of them went south a while back, it took hours
and hours to get it restored. With RAID arrays, of course, that's not
supposed to happen; I think it was a problem with an SVC.
On the mainframe we take frequent full volume backups. The likelihood of
true failover (DR) is minuscule, and we use XRC mirroring for that
contingency anyway. On the other hand the probability of having to retrieve
an accidentally deleted or modified file is huge--it happens all the time
even for sysprog finger checks.
1. How long does it take to make a tape backup of a 32760 cylinder volume?
2. Where does that backup live?
3. How long does it take to restore a critical 10 track file from two weeks
ago that happens to live on the corner of cylinder 31753?
.
--
| Jim Phoenix | Voice: (310) 338-0400 x316 |
| Senior Software Developer | Fax: (310) 338-0801 |
| Phoenix Software International | Alt fax: (310) 337-2685 |
| 5200 W. Century Blvd., Suite 800 | [EMAIL PROTECTED] |
| Los Angeles, CA 90045 | http://www.phoenixsoftware.com |
Opinions expressed by this individual are not necessarily those of the Company.
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