Hi, Steve.

At 04:40 PM 9/30/98 -0700, Steve Widmar wrote:
>Rumour (am I british? I mean 'rumor') has it that DDS3 drives can read DDS2
>tapes and if a DDS2 tape is in the drive when a DDS3 drive is writing to that
>drive, the DDS2 tape can then be read by some other DDS2 drive.
>
>All of this with no software or hardware config, just using the correct tape.
>
>Truth?

That's the plan.

Here's the general facts, though some drive and media vendors might have
exceptions to this, the DDS standards claim these features:

All DDS media (except DAT and early DDS-1 tapes without MRS, "Media
Recognition System") has a method of informing the tape drive what type of
DDS media it is, that is whether it's DDS-1, DDS-2, DDS-3 or whatever.  The
DDS-2 and higher drives use the lower density recording modes automatically
when writing to lower density media.  The only exception is that DDS-DC
drives (DDS-1 plus firmware data compression) write only to DDS-1 media but
normally compress the data which can then only be read back on a DDS-DC or
DDS-2 or later drive.  (Only the early pre-DDS-DC drives didn't support
data compression.)

So the bottom line is that (with the exception of data compression support
on early DDS-1 drives) any DDS media (with MRS, as all DDS-2 media and
above require) should be readable on any DDS drive which supports that
media format even when the media was written on with a higher capability
drive.  In other words, any DDS-2 drive should be able to read any DDS-2
tape regardless of what kind of drive wrote on it.  The DDS-3 drive should
fall back to write in DDS-2 format in that case.
--
Jeff Woods
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