More Streaming device questions

Kevin D Butt kdbutt at us.ibm.com
Thu Aug 26 09:52:06 PDT 2004


* From the T10 Reflector (t10 at t10.org), posted by:
* Kevin D Butt <kdbutt at us.ibm.com>
*
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Burn, 

You do not need to set the block size in the mode header to 0 before you
can use variable block transfers.  Just set the fixed bit in CDB to 0. 

Kevin D. Butt
Fibre Channel & SCSI Architect, IBM Tape Microcode, 
6TYA, 9000 S. Rita Rd., Tucson, AZ  85744
Tie-line 321; Office: 520-799-5280, Lab: 799-5751, Fax: 799-4138, Email:
kdbutt at us.ibm.com 



Burn Alting <burn at goldweb.com.au> 
Sent by: owner-t10 at t10.org 


08/25/2004 03:35 AM 

To
t10 at t10.org 

cc

Subject
More Streaming device questions

	





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

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

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.

Burn

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<br><font size=2 face="sans-serif">Burn,</font>
<br>
<br><font size=2 face="sans-serif">You do not need to set the block size
in the mode header to 0 before you can use variable block transfers. &nbsp;Just
set the fixed bit in CDB to 0.</font>
<br><font size=2 face="sans-serif"><br>
Kevin D. Butt<br>
Fibre Channel &amp; SCSI Architect, IBM Tape Microcode, <br>
6TYA, 9000 S. Rita Rd., Tucson, AZ &nbsp;85744<br>
Tie-line 321; Office: 520-799-5280, Lab: 799-5751, Fax: 799-4138, Email:
kdbutt at us.ibm.com</font>
<br>
<br>
<br>
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<td width=40%><font size=1 face="sans-serif"><b>Burn Alting <burn at goldweb.com.au&gt;</b>
</font>
<br><font size=1 face="sans-serif">Sent by: owner-t10 at t10.org</font>
<p><font size=1 face="sans-serif">08/25/2004 03:35 AM</font>
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<div align=right><font size=1 face="sans-serif">To</font></div>
<td valign=top><font size=1 face="sans-serif">t10 at t10.org</font>
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<div align=right><font size=1 face="sans-serif">cc</font></div>
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<td>
<div align=right><font size=1 face="sans-serif">Subject</font></div>
<td valign=top><font size=1 face="sans-serif">More Streaming device questions</font></table>
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<br>
<br><font size=2><tt>* From the T10 Reflector (t10 at t10.org), posted by:<br>
* Burn Alting <burn at goldweb.com.au&gt;<br>
*<br>
* From the T10 Reflector (t10 at t10.org), posted by:<br>
* Burn Alting <burn at goldweb.com.au&gt;<br>
*<br>
Yet more questions.<br>
<br>
When I start my tape target, I set the logical block size to a default<br>
value.<br>
<br>
For my block limits, I set my minimum block length to 512 and my maximum<br>
to some large multiple of 512 bytes and since I want all IO in 512-byte<br>
quantities, I set the granularity field to be 9 (ie 2^9 = 512).<br>
<br>
If I want to perform IO in variable block mode, am I required to first<br>
set the logical block size (via a Mode Select changing the Block Length<br>
field in the Mode Parameter Block Descriptor) to zero and then issue my<br>
Read or Write commands with the fixed bit set to zero and the transfer<br>
length to be the number of bytes I want to transfer?<br>
<br>
If this is the case, ie I have set the logical block size to 0, what<br>
happens if a read or write command has it's fixed bit set to 1?<br>
<br>
Regards and thanks to all those who have been replying to my questions.<br>
<br>
Burn<br>
<br>
*<br>
* For T10 Reflector information, send a message with<br>
* 'info t10' (no quotes) in the message body to majordomo at t10.org<br>
*<br>
* For T10 Reflector information, send a message with<br>
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<br>
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