At 04:20 PM 3/12/98 -0500, Wayne, Roby wrote:
>We just upgraded from a C1503B DDS to a C1504B DDS2, supposedly.  Do
>these "little babies" support 120m tapes?  So far, we haven't seen any
>marked improvement in the upgrade.

The C1503B is a DDS-1 drive; the C1504B is the (I believe) same mechanism
with a firmware upgrade which adds "hardware compression" (which is really
done in firmware) making it a DDS-DC drive.  Both drives support 90m and
shorter tapes only, and have a theoretical maximum transfer rate of
183KB/second.  (The DDS-DC drive may see an effective rate higher because
of the effect of compressing the data.)  90m tapes yield 2GB native (which
means ignoring compression).  Shorter tapes use the same recording format
which therefore yields linearly proportional capacities.  For example, 60m
tapes are 1.3 GB native.

On the other hand, DDS-2 drives not only can write data to 120m tapes at a
higher density yielding 4GB native per tape, they read and write all tapes
at substantially higher speeds than the DDS-1 or DDS-DC drives.  DDS-3
drives (which also support DDS-2 media) are even faster and "bigger"
writing 12GB native per 125m tape.  All DDS-2 and DDS-3 drives that I have
heard of support firmware data compression.

Bottom line is that the C1504B is basically just a C1503B plus firmware
compression.  They only support 90m and shorter tapes.
--
Jeff Woods
[log in to unmask] at Tivoli Systems
[log in to unmask]   at home  [PGP key available here via finger]

Haiku by Rahul Sonnad:
   There is a chasm
   of carbon and silicon
   the software can't bridge.