Maximum SAS devices

Johnson, Stephen B. sjohnson at lsil.com
Tue Sep 30 06:52:34 PDT 2003


* From the T10 Reflector (t10 at t10.org), posted by:
* "Johnson, Stephen B." <sjohnson at lsil.com>
*
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Actually, the spec (revision 5) says an edge expander device set can
have a maximum of 128 SAS Addresses (not physical links) and a Fanout
can have 128 edge expander sets or 128 end devices. With wide ports 128
links can easily be exceeded and this is perfectly legal. 
Wide links do not reduce the maximum number since the wide links share
the same SAS address.
 
So, the max number of SAS addresses in a single domain is 128 * 128 =
16384
The max number of phys is much larger depending on the size and number
of wide links.
 
Steve
 
-----Original Message-----
From: Czekalski, Marty [mailto:Marty_Czekalski at maxtor.com]
Sent: Tuesday, September 30, 2003 6:30 AM
To: 'EGR'
Cc: Lea Schwartz (E-mail); T10 at t10.org
Subject: RE: Maximum SAS devices


The FAQs were done about a year and a half ago and reflected what the
goal was at the time.  As the spec was finalized and the fields defined
in detail, it was possible to allow up to 128 physical links per
expander.   The number of devices will be less than 128 if wide links
are used. The FAQs need to be updated.
 
Marty

-----Original Message-----
From: EGR [mailto:egr_mail at yahoo.com]
Sent: Monday, September 29, 2003 4:44 PM
To: T10 at t10.org
Subject: Maximum SAS devices



Hi all,

 

Quick question on SAS.  

The SCSI Trade Association SAS FAQ (point 5) indicates that an expander
can address a maximum of 64 devices and there is a maximum of 4096
devices in a domain.

I can't find anything in the spec that indicates the above. 

In fact, the spec indicates that the maximum number of SAS addressed
used by an expander is 128.

 

Is the FAQ incorrect, or am I missing something?

 

Thanks,

 

Elizabeth Rodriguez

 


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Wide links do not reduce the maximum number since the wide links share the same SAS address.
  
 So, the max number of SAS addresses in a single domain is 128 * 128 = 16384
 The max number of phys is much larger depending on the size and number of wide links.
  
 Steve
  
 -----Original Message-----
From: Czekalski, Marty [mailto:Marty_Czekalski at maxtor.com]
Sent: Tuesday, September 30, 2003 6:30 AM
To: 'EGR'
Cc: Lea Schwartz (E-mail); T10 at t10.org
Subject: RE: Maximum SAS devices


 The FAQs were done about a year and a half ago and reflected what the goal was at the time.  As the spec was finalized and the fields defined in detail, it was possible to allow up to 128 physical links per expander.   The number of devices will be less than 128 if wide links are used. The FAQs need to be updated.
  
 Marty
 -----Original Message-----
From: EGR [mailto:egr_mail at yahoo.com]
Sent: Monday, September 29, 2003 4:44 PM
To: T10 at t10.org
Subject: Maximum SAS devices


 Hi all,   Quick question on SAS.  The SCSI Trade Association SAS FAQ (point 5) indicates that an expander can address a maximum of 64 devices and there is a maximum of 4096 devices in a domain. I can't find anything in the spec that indicates the above. In fact, the spec indicates that the maximum number of SAS addressed used by an expander is 128.   Is the FAQ incorrect, or am I missing something?   Thanks,   Elizabeth Rodriguez  


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