legal but rude

Robert Snively rsnively at brocade.com
Mon Feb 24 06:35:41 PST 2003


* From the T10 Reflector (t10 at t10.org), posted by:
* Robert Snively <rsnively at brocade.com>
*
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Sounds like time for somebody to take on the task 
of creating some profiles. 

Bob 

> -----Original Message----- 
> From: JimMcGrath at oaktech.com [ mailto:JimMcGrath at oaktech.com
 ] 
> Sent: Friday, February 21, 2003 4:13 PM 
> To: JimMcGrath at oaktech.com 
> Cc: LAVARRE at iomega.com; owner-t10 at t10.org; t10 at t10.org 
> Subject: Re: legal but rude 
> 
> 
> * From the T10 Reflector (t10 at t10.org), posted by: 
> * JimMcGrath at oaktech.com 
> * 
> 
> 
> 
> 
> 
> 
> BTW, I agree with Pat and Ken that just compliance to a 
> standard is not 
> adequate for a good supplier - one needs also to look into 
> the particulars 
> of your target customers.  But this can be quite different 
> from designing 
> to "what everyone knows."   And while designing above and beyond the 
> requirements of a standard is a good practice, designing at least to a

> standard is really a necessary practice in this interoperable world. 
> 
> That's my biggest objection - the belief that some parties in 
> the industry 
> (e.g. host manufacturers) don't need to adhere to a 
> documented standard 
> like everyone else.  In theory the interface standards are 
> equally binding 
> on host and device.  In practice hosts often feel able to 
> ignore a standard 
> entirely. 
> 
> The block size issue is actually a good example.  If 
> "everyone knows" that 
> you cannot use a block size > 4Kbytes, then why is not that 
> in the standard 
> (afterall, we put in lots of limits)?  I suspect the issue is 
> either the 
> fact that it is NOT an "everyone knows" item, or it is one, 
> but no one with 
> that knowledge bothers to contributes to standards 
> development.  On this 
> particular issue I suspect the former, but in other cases it 
> could very 
> well be the latter.  In either case, I would place a lesser 
> share of the 
> blame on device developers. 
> 
> Jim 
> 
> 
> 
>                                                               
>                                                               
>            
>                       JimMcGrath at oaktec                       
>                                                               
>            
>                       h.com                    To:       
> LAVARRE at iomega.com                                            
>                 
>                       Sent by:                 cc:       
> owner-t10 at t10.org, t10 at t10.org                                
>                 
>                       owner-t10 at t10.org        Subject:  Re: 
> legal but rude                                                
>             
>                                                               
>                                                               
>            
>                                                               
>                                                               
>            
>                       02/21/2003 01:08                        
>                                                               
>            
>                       PM                                      
>                                                               
>            
>                                                               
>                                                               
>            
>                                                               
>                                                               
>            
> 
> 
> 
> 
> * From the T10 Reflector (t10 at t10.org), posted by: 
> * JimMcGrath at oaktech.com 
> * 
> 
> 
> 
> 
> 
> 
> Pat, 
> 
> That problem is with the "everyone knows" that hosts expect 
> block sizes to 
> be <= 4KBytes.  As you point out, that is not generally 
> documented anywhere 
> (in, for instance, a standard), and so it is not clear that "everyone 
> knows."  Indeed, the reason why devices have standards to 
> begin with is 
> that it is not reasonable to expect all host designers to know what 
> "everyone knows" about devices.  So it is with respect to 
> device designers 
> with respect to hosts. 
> 
> Bottom line is that the purposes of documents is to, well, document. 
> Unless something is documented, it is not reasonable to 
> expect designers to 
> magically "know" about something (especially if it is debatable as to 
> whether that knowledge is actually true).  It is certainly 
> not reasonable 
> to expect a procurement organization to request compliance with "what 
> everyone knows" (as opposed to a standard) to insure compatibility. 
> 
> Jim 
> 
> 
> 
> 
> 
>                       "Pat LaVarre" 
> 
>                       <LAVARRE at iomega.c        To:       <t10 at t10.org>

> 
>                       om>                      cc: 
> 
>                       Sent by:                 Subject:  
> legal but rude 
> 
>                       owner-t10 at t10.org 
> 
> 
> 
>                       02/21/2003 10:28 
> 
>                       AM 
> 
> 
> 
> 
> 
> 
> 
> * From the T10 Reflector (t10 at t10.org), posted by: 
> * "Pat LaVarre" <LAVARRE at iomega.com> 
> * 
> By the way, I find a number of engineers find the "legal but 
> rude" concept 
> difficult to learn. 
> 
> Anybody got a better way to explain it? 
> 
> The kind of design I mean by this phrase includes choosing 
> plug 'n play 
> descriptors, such as op x12 Inquiry data, formed strictly in 
> accord with 
> the merely public merely standard paper specs ... that in fact don't 
> interoperate well because they aren't normal.  Of course I 
> can't easily 
> discuss any real & current examples, but here's an analogous 
> hypothetical. 
> 
> Suppose someone actually built a device with an op x12 Inquiry that 
> returned x00 DASD as the byte 0 & x1F PDT 
> (PeripheralDeviceType) but then 
> responded to op x25 ReadCapacity with a blockLength larger 
> than x1000 B = 
> 4KiB. 
> 
> All the paper specs say this is utterly legit.  But if you actually go

> build such a thing, the host i/o chokes, because "everyone 
> knows" that the 
> block size of any HDD is supposed to be as small or smaller 
> than a virtual 
> memory page, and "almot everyone knows" that the block size 
> of x00 DASD is 
> supposed to be x200 B = 512 B = 0.5KiB. 
> 
> I say the device and the host here are being "rude".  This 
> other engineer 
> said only the host was "rude", because the paper spec covers 
> the device, so 
> the device is "legal", and there is no paper spec for the host.  I say

> neither would have got caught being rude if the other had 
> been polite.  I 
> say we know they are mutually rude because the system breaks, 
> despite half 
> of the system, the device, being completely legal by any 
> reasonable reading 
> of the merely public merely standard paper specs. 
> 
> What can this engineer be thinking, to say only the host is rude? 
> 
> How can I explain that the device here is equally rude? 
> 
> Cluelessly, curiously, thankfully yours, and a Happy Friday 
> to you, Pat 
> LaVarre 
> 
> P.S. If by chance I err and some paper spec does tell us that 
> block size 
> other than 0.5 KiB isn't legal for PDT = x00 DASD, that 
> rather misses the 
> point.  The point is we can tell it's rude before we even ask if it's 
> legal. 
> 
> * 
> * For T10 Reflector information, send a message with 
> * 'info t10' (no quotes) in the message body to majordomo at t10.org 
> 
> 
> 
> * 
> * For T10 Reflector information, send a message with 
> * 'info t10' (no quotes) in the message body to majordomo at t10.org 
> 
> 
> 
> * 
> * For T10 Reflector information, send a message with 
> * 'info t10' (no quotes) in the message body to majordomo at t10.org 
> 


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 RE: legal but rude Sounds like time for somebody to take on the task 
of creating some profiles. Bob > -----Original Message----- 
> From: JimMcGrath at oaktech.com [mailto:JimMcGrath at oaktech.com] 
> Sent: Friday, February 21, 2003 4:13 PM 
> To: JimMcGrath at oaktech.com 
> Cc: LAVARRE at iomega.com; owner-t10 at t10.org; t10 at t10.org 
> Subject: Re: legal but rude 
> 
> 
> * From the T10 Reflector (t10 at t10.org), posted by: 
> * JimMcGrath at oaktech.com 
> * 
> 
> 
> 
> 
> 
> 
> BTW, I agree with Pat and Ken that just compliance to a 
> standard is not 
> adequate for a good supplier - one needs also to look into 
> the particulars 
> of your target customers.  But this can be quite different 
> from designing 
> to ;what everyone knows.;   And while designing above and beyond the 
> requirements of a standard is a good practice, designing at least to a 
> standard is really a necessary practice in this interoperable world. 
> 
> That's my biggest objection - the belief that some parties in 
> the industry 
> (e.g. host manufacturers) don't need to adhere to a 
> documented standard 
> like everyone else.  In theory the interface standards are 
> equally binding 
> on host and device.  In practice hosts often feel able to 
> ignore a standard 
> entirely. 
> 
> The block size issue is actually a good example.  If 
> ;everyone knows; that 
> you cannot use a block size > 4Kbytes, then why is not that 
> in the standard 
> (afterall, we put in lots of limits)?  I suspect the issue is 
> either the 
> fact that it is NOT an ;everyone knows; item, or it is one, 
> but no one with 
> that knowledge bothers to contributes to standards 
> development.  On this 
> particular issue I suspect the former, but in other cases it 
> could very 
> well be the latter.  In either case, I would place a lesser 
> share of the 
> blame on device developers. 
> 
> Jim 
> 
> 
> 
>                                                               
>                                                               
>            
>                       JimMcGrath at oaktec                       
>                                                               
>            
>                       h.com                    To:       
> LAVARRE at iomega.com                                            
>                 
>                       Sent by:                 cc:       
> owner-t10 at t10.org, t10 at t10.org                                
>                 
>                       owner-t10 at t10.org        Subject:  Re: 
> legal but rude                                                
>             
>                                                               
>                                                               
>            
>                                                               
>                                                               
>            
>                       02/21/2003 01:08                        
>                                                               
>            
>                       PM                                      
>                                                               
>            
>                                                               
>                                                               
>            
>                                                               
>                                                               
>            
> 
> 
> 
> 
> * From the T10 Reflector (t10 at t10.org), posted by: 
> * JimMcGrath at oaktech.com 
> * 
> 
> 
> 
> 
> 
> 
> Pat, 
> 
> That problem is with the ;everyone knows; that hosts expect 
> block sizes to 
> be <= 4KBytes.  As you point out, that is not generally 
> documented anywhere 
> (in, for instance, a standard), and so it is not clear that ;everyone 
> knows.;  Indeed, the reason why devices have standards to 
> begin with is 
> that it is not reasonable to expect all host designers to know what 
> ;everyone knows; about devices.  So it is with respect to 
> device designers 
> with respect to hosts. 
> 
> Bottom line is that the purposes of documents is to, well, document. 
> Unless something is documented, it is not reasonable to 
> expect designers to 
> magically ;know; about something (especially if it is debatable as to 
> whether that knowledge is actually true).  It is certainly 
> not reasonable 
> to expect a procurement organization to request compliance with ;what 
> everyone knows; (as opposed to a standard) to insure compatibility. 
> 
> Jim 
> 
> 
> 
> 
> 
>                       ;Pat LaVarre; 
> 
>                       <LAVARRE at iomega.c        To:       <t10 at t10.org> 
> 
>                       om>                      cc: 
> 
>                       Sent by:                 Subject:  
> legal but rude 
> 
>                       owner-t10 at t10.org 
> 
> 
> 
>                       02/21/2003 10:28 
> 
>                       AM 
> 
> 
> 
> 
> 
> 
> 
> * From the T10 Reflector (t10 at t10.org), posted by: 
> * ;Pat LaVarre; <LAVARRE at iomega.com> 
> * 
> By the way, I find a number of engineers find the ;legal but 
> rude; concept 
> difficult to learn. 
> 
> Anybody got a better way to explain it? 
> 
> The kind of design I mean by this phrase includes choosing 
> plug 'n play 
> descriptors, such as op x12 Inquiry data, formed strictly in 
> accord with 
> the merely public merely standard paper specs ... that in fact don't 
> interoperate well because they aren't normal.  Of course I 
> can't easily 
> discuss any real & current examples, but here's an analogous 
> hypothetical. 
> 
> Suppose someone actually built a device with an op x12 Inquiry that 
> returned x00 DASD as the byte 0 & x1F PDT 
> (PeripheralDeviceType) but then 
> responded to op x25 ReadCapacity with a blockLength larger 
> than x1000 B = 
> 4KiB. 
> 
> All the paper specs say this is utterly legit.  But if you actually go 
> build such a thing, the host i/o chokes, because ;everyone 
> knows; that the 
> block size of any HDD is supposed to be as small or smaller 
> than a virtual 
> memory page, and ;almot everyone knows; that the block size 
> of x00 DASD is 
> supposed to be x200 B = 512 B = 0.5KiB. 
> 
> I say the device and the host here are being ;rude;.  This 
> other engineer 
> said only the host was ;rude;, because the paper spec covers 
> the device, so 
> the device is ;legal;, and there is no paper spec for the host.  I say 
> neither would have got caught being rude if the other had 
> been polite.  I 
> say we know they are mutually rude because the system breaks, 
> despite half 
> of the system, the device, being completely legal by any 
> reasonable reading 
> of the merely public merely standard paper specs. 
> 
> What can this engineer be thinking, to say only the host is rude? 
> 
> How can I explain that the device here is equally rude? 
> 
> Cluelessly, curiously, thankfully yours, and a Happy Friday 
> to you, Pat 
> LaVarre 
> 
> P.S. If by chance I err and some paper spec does tell us that 
> block size 
> other than 0.5 KiB isn't legal for PDT = x00 DASD, that 
> rather misses the 
> point.  The point is we can tell it's rude before we even ask if it's 
> legal. 
> 
> * 
> * For T10 Reflector information, send a message with 
> * 'info t10' (no quotes) in the message body to majordomo at t10.org 
> 
> 
> 
> * 
> * For T10 Reflector information, send a message with 
> * 'info t10' (no quotes) in the message body to majordomo at t10.org 
> 
> 
> 
> * 
> * For T10 Reflector information, send a message with 
> * 'info t10' (no quotes) in the message body to majordomo at t10.org 
> 
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