Lee observed......

>
>For anyone who's interested in using DLT on the HP3000:
>
>We just installed two Digital TZ-88 20/40 GByte DLT's on our 992-400
>for evaluation, and initial tests are very promising.  Both are
>daisy-chained to one (1) SE SCSI adapter, for now, and are
>host-configured as HPC1520B DDS-2 drives.  We've run several small
>store/restore tests using NM STORE/RESTORE, CM STORE/RESTORE and Orbit
>'BackupPlus' STORE/RESTORE.  In the latter case, we set up our full
>system backup one evening to use the DLTs in parallel, and the backup
>took 4.75 hours and consumed 2 DLT cartridges (approximately 81 Gbytes
>stored).  Compression was done on the host (COMPRESS=3), and
>approximately a 4:1 factor was achieved.  Our current backup to two
>7980XC open-reel drives takes approximately 8 hours and consumes 90-100
>2400' reels (same compression factor).
>

As a comparison one of my clients uses four DDS drives in parallel with
Turbostore on a 959/400.
They backup about 22GB in about 90 minutes (1h30) onto four 120m DAT
cartridges.
Only hardware compression is used.

So by extrapolation, 88GB would take 6Hrs to four drives (4 x 1h30), but
would have to be attended to perform a DAT swap, and maybe only 3 hours
to eight drives in parallel, unattended. Or even 4h30 to 6 drives also
unattended since 88GB / 6 = 14.6 GB per DAT.

I wonder what the difference in cost is for the drives and media, DDS vs
DLT.

I'd be looking for a quantum leap in backup technology, say like the
difference between the old Cartridge and the 7980XC before recommending
a shift away from DDS. Maybe we'll get solid state backups in five years
- or liquid memory :)

Just thoughts

Neil

Neil Harvey
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+27 21 221907