Comments on T10 proposal 05-101r1 (part 2)

George Penokie gop at us.ibm.com
Tue May 17 14:53:12 PDT 2005


* From the T10 Reflector (t10 at t10.org), posted by:
* George Penokie <gop at us.ibm.com>
*
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Gerry, 

I addition, if you require the FFFFh value in the application tag to
disable all write checking then you are requiring an application client
to make sure it sets the application tag to some value other than FFFFh,
even if it has no use for the application tag. That would be the case
because the default value for the application tag is FFFFh and if the
application client does nothing to change it then any write checking it
expected would not occur. That's not very user friendly. So you better
have a good reason for putting that requirement on applications. 

Bye for now,
George Penokie

Dept 2C6  114-2 N212
E-Mail:    gop at us.ibm.com
Internal:  553-5208
External: 507-253-5208   FAX: 507-253-2880





Gerry.Houlder at seagate.com 
Sent by: owner-t10 at t10.org 


05/17/2005 03:19 PM 

To
t10 at t10.org 

cc

Subject
Comments on T10 proposal 05-101r1

	





* From the T10 Reflector (t10 at t10.org), posted by:
* Gerry.Houlder at seagate.com
*
This proposal adds wording that states "A LOGICAL BLOCK APPLICATION TAG
field set to FFFFh disables checking of all protection information for
the
logical block when reading from the medium."

I don't believe this restriction is a good idea. This disabling of all
checking should also occur for writes as well.

Consider design of target hardware to implement this function. The
hardware
needs to be designed so that an Application Tag value of FFFFh overrides
any checking that would otherwise be permitted by the RDPROTECT field in
the CDB. Now imagine that the same hardware will be used for checking
data
|from a WRITE command. Is it reasonable that the target should redesign
the
same hardware so that  the WRPROTECT field overrides the Application Tag
value of FFFFh? We don't think so.

If there is another reason (other than just making the wording more
specific) I'd like to hear it. Otherwise I would like to see this change
withdrawn or I make a new proposal that changes the wording to "either
writing or reading".

*
* For T10 Reflector information, send a message with
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<br><font size=2 face="sans-serif">Gerry,</font>
<br>
<br><font size=2 face="sans-serif">I addition, if you require the FFFFh
value in the application tag to disable all write checking then you are
requiring an application client to make sure it sets the application tag
to some value other than FFFFh, even if it has no use for the application
tag. That would be the case because the default value for the application
tag is FFFFh and if the application client does nothing to change it then
any write checking it expected would not occur. That's not very user friendly.
So you better have a good reason for putting that requirement on applications.</font>
<br><font size=2 face="sans-serif"><br>
Bye for now,<br>
George Penokie<br>
<br>
Dept 2C6 &nbsp;114-2 N212<br>
E-Mail: &nbsp; &nbsp;gop at us.ibm.com<br>
Internal: &nbsp;553-5208<br>
External: 507-253-5208 &nbsp; FAX: 507-253-2880<br>
<br>
</font>
<br>
<br>
<br>
<table width=100%>
<tr valign=top>
<td width=40%><font size=1 face="sans-serif"><b>Gerry.Houlder at seagate.com</b>
</font>
<br><font size=1 face="sans-serif">Sent by: owner-t10 at t10.org</font>
<p><font size=1 face="sans-serif">05/17/2005 03:19 PM</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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<td>
<div align=right><font size=1 face="sans-serif">cc</font></div>
<td valign=top>
<tr>
<td>
<div align=right><font size=1 face="sans-serif">Subject</font></div>
<td valign=top><font size=1 face="sans-serif">Comments on T10 proposal
05-101r1</font></table>
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<table>
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<td>
<td></table>
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<br>
<br>
<br><font size=2><tt>* From the T10 Reflector (t10 at t10.org), posted by:<br>
* Gerry.Houlder at seagate.com<br>
*<br>
This proposal adds wording that states "A LOGICAL BLOCK APPLICATION
TAG<br>
field set to FFFFh disables checking of all protection information for
the<br>
logical block when reading from the medium."<br>
<br>
I don't believe this restriction is a good idea. This disabling of all<br>
checking should also occur for writes as well.<br>
<br>
Consider design of target hardware to implement this function. The hardware<br>
needs to be designed so that an Application Tag value of FFFFh overrides<br>
any checking that would otherwise be permitted by the RDPROTECT field in<br>
the CDB. Now imagine that the same hardware will be used for checking data<br>
|from a WRITE command. Is it reasonable that the target should redesign
the<br>
same hardware so that &nbsp;the WRPROTECT field overrides the Application
Tag<br>
value of FFFFh? We don't think so.<br>
<br>
If there is another reason (other than just making the wording more<br>
specific) I'd like to hear it. Otherwise I would like to see this change<br>
withdrawn or I make a new proposal that changes the wording to "either<br>
writing or reading".<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>
</tt></font>
<br>
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