OSD_Perspective

Dal Allan endlcom at acm.org
Wed Aug 16 13:40:27 PDT 2000


* From the T10 Reflector (t10 at t10.org), posted by:
* "Dal Allan" <endlcom at acm.org>
*
Hi Jim and Dave,

Jim hit the nail on the head, but bent the nail.

> 1) I look at an OSD as a simplified NFS, not a glorified disk drive.  
>    You look at it the other way around.

These are not opposing views they are complementary. 

This is actually an agreement, because both you and Dave have valid views of 
the world. 

> 2) As a simplified NFS, TCP/IP is the natural protocol. 
>    As a glorified disk, SCSI is the natural one.

Yep, and here's why both are needed:

 - Those of us involved with standards are in the technology enabling 
   business. 

 - Creating products that change the way things have been done in 
   the past is done by opportunists who see economic benefit. 

 - The decision on SCSI OSD vs NFS OSD will probably be based on what 
   kind of experience the implementors/visionaries have rather than 
   what makes the best fit to their market objective.

 - None of us can predict the 'best' use of OSD.

 - Even if you get the last one right by accident, it does not mean you
   can pick which company will make the most money from implementing OSD. 

Since I am waxing philosophical, a few words on the religious issue of 
bidirectional SCSI. 

SCSI came into the world as an interface to make low end disk drives easier 
to integrate. Look at the origins in SASI and think Kentucky Fried, 'cheap, 
cheap, cheap...' 

There was no architectural merit or benefit to leaving bidirectional 
transfers out, it was because they cost more. 

Over the past umpteen years, most of the problems created by the emphasis on 
cheap have been corrected (Autosense as the most obvious but there is a long 
list of others). It's about time we added bidirectional transfers, so I'll 
be in Quixote Penokie's corner next month, holding the towel and urging him 
on. 

All the best,

Dal
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