More Streaming device questions

Burn Alting burn at
Wed Aug 25 03:35:59 PDT 2004

* From the T10 Reflector (t10 at, posted by:
* Burn Alting <burn at>
Yet more questions.

When I start my tape target, I set the logical block size to a default

For my block limits, I set my minimum block length to 512 and my maximum
to some large multiple of 512 bytes and since I want all IO in 512-byte
quantities, I set the granularity field to be 9 (ie 2^9 = 512).

If I want to perform IO in variable block mode, am I required to first
set the logical block size (via a Mode Select changing the Block Length
field in the Mode Parameter Block Descriptor) to zero and then issue my
Read or Write commands with the fixed bit set to zero and the transfer
length to be the number of bytes I want to transfer?

If this is the case, ie I have set the logical block size to 0, what
happens if a read or write command has it's fixed bit set to 1?

Regards and thanks to all those who have been replying to my questions.


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