Thanks to all that replied my initial mail:
>Hello osf-managers,
>
> Our site is contemplating the purcahse of a 9 GB drive to do evening
> level one backups. Has anyone used this strategy before? I'm thinking
> the money may be better spent on a multiple-tape tape drive. Any
> suggestions/evaluations would be greatly appreciated. I will
> summerize.
>
>Steve McLaughlin Unix Sysadmin
>mclaughl_at_nssdc.gsfc.nasa.gov (301) 725-2632
>
Here are some of the responses:
From: alan_at_nabeth.cxo.dec.com
I've used disks as a staging area for backups, but those
were always then backed up to tape for offsite and archival
storage. Backing up to disk might have a speed advantage
or many streaming tapes. With both disk and tape you have
to make the choice of making temporary backups that constantly
get overwritten or doing archival backups. If doing archival
backups to disk, the disk will fill up eventually and you
either have to migrate the data or buy a bigger disk. With
tapes you just buy more tapes and for their capacity tapes
are cheap, even if the drive costs more up front.
From: "Paul E. Rockwell" <rockwell_at_rch.dec.com>
Pros:
It's cheaper than a tape drive
It may be faster than backing up to a tape drive. However the new generation
of tape drives are pretty darned fast. The DLT technology in particular
in Digital's TZ87 family can back up up to 2.5MB/sec. 20GB on one cartridge.
Cons:
Capacity. You can't back up more than 9GB.
Disaster recovery. Pretty hard (and expensive) to move the backup off
site to provide for disaster recovery. With a tape, just take a relatively
low cost cartridge off site. Sure beats taking a $2000+ drive away.
You won't be able to get at older versions of the backup. How would you
answer the question: I want the file back that I deleted 1 week ago?
Robustness. If you lose that disk, you've lost your backup. And with no
other backup medium, you're dead in the water.
I'd get the tape drive (especially a jukebox) if I were you, and consider
using a product such as Polycenter NetWorker Save and Restore to do your
backups - something that can manage your jukebox and automate your backup
strategy.
From: Dave Sill <de5_at_sws5.CTD.ORNL.GOV>
Even better: a DLT 2000 tape drive that can hold 10GB without
compression.
From: "Andreas Burkhardtsmaier" <burkh_at_str.daimler-benz.com>
I don't know how big your Level 1 Backups are, but keep in mind your not able
to keep a backup over a period of time. At our site we are using tape drives, a
Backup is archived for two weeks, 1 tape per month is archived for two years, 1
tape per year is archived forever.
From: Fred Lance <f_lance_at_tec.nh.us>
We prefer tape as we move the tapes off-site daily to provide recovery in
the case of fire or water damage. This could be done with disk, but not
as cheaply!
From: Jim Belonis <belonis_at_dirac.phys.washington.edu>
Purchases should be decided on based on maximum load (i.e. level 0).
Then use what you have.
We have a 10-tape jukebox so we can do a couple days of backup unattended.
We do about 50gig of level 0 dumps every month which takes several days.
We have a second tape drive in case the first breaks.
We do incremental level 1 every weekend and level 2 every night.
The level 2 takes about 3-4 hours.
We don't use the tape for anything else, so who cares if it is always
occupied ?
It is more efficient tape-time-wise to do the incremental to a disk, then
copy from disk to tape quickly. This helps the tape keep streaming.
But we don't do that.
From: alby_at_iconz.co.nz (Alby Cartner)
My main concern is that with a single device you only need one point of
failure to lose it all. e.g. Air conditioning failure cooks all the drives
on site!!!
And it is hard to move it off site.
With level one, I assume daily. That means you will still be doing weekly
to tape that can be taken off site to secure against fire risk???
Will 9 Gb give you multiple backups before it is full? Or do you overwrite
each night. On second scenario what happens if the file system trashes
itself half way through the backup? (not implying that OSF would ever do
that ;) ) What part of the backup is current, and what is old ??? . If you
run databases this will be absolutely critical! ( The backup will be worse
than useless otherwise)
Received on Mon Jun 26 1995 - 23:26:27 NZST