On 10/28/2014 01:04 PM, Alan Brown wrote:
> 
> Block devices may be block devices, but a tape drive is a character device.

Oops. Works either way, disks are char aka "raw" devices too.

> People coming from a tape environment tend to see tapes (volumes) as
> something you use for a pool of clients or filesets, because changing
> volumes is NOT trivial, the tapes are only reated for a limited number
> of load cycles and you can only access one volume at a time.
> 
> If you have more tape drives you can access more volumes simultaneously,
> but changing volumes is no less difficult/timeconsuming.

As is changing disks. Skipping from one tarball to another on tape may
take much longer, but that shouldn't make any difference to the
higher-level code.

There is no reason to see file volumes as dedicated to a client AFAICT;
those who want it can do pool per client and volumes per pool -- works
with tapes just as well.

Yes, in general you can access multiple files on the same disk
simultaneously. I don't expect that a backup application streaming data
to or from that disk would -- or should -- actually do that, for any
number of obvious reasons.

Which is why I'll never understand the tape/disk dichotomy.

(As an aside, bacula, specifically, seems to force you to use different
Media Type for each physical device so I don't get how it would work
with multiple drives in the same jukebox, either -- thankfully I don't
need to.)
-- 
Dimitri Maziuk
Programmer/sysadmin
BioMagResBank, UW-Madison -- http://www.bmrb.wisc.edu

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