SAS-2 rev.15 Missing Sync lost message definition
Elliott, Robert (Server Storage)
Elliott at hp.com
Wed Dec 3 11:30:22 PST 2008
* From the T10 Reflector (t10 at t10.org), posted by:
* "Elliott, Robert (Server Storage)" <Elliott at hp.com>
DWS Lost is the name of a message going to SP, not the SP receiver. They're
sent at similar times and possibly could be made identical.
Although the SAS standard (like most other serial protocols) only requires a
BER of 10^12 (which is one error every 2.77 min per one direction of a
physical link at 6 Gbps), a system generating anywhere near those number of
errors will have so many other problems it won't be viable. Dword
synchronization mainly just happens once during speed negotiation. Most of
the time is spent finding the center of the bits; once done, identifying the
dword boundary by finding a comma is easy.
From: Samek [mailto:samek at halstor.com]
Sent: Tuesday, December 02, 2008 6:13 PM
To: Elliott, Robert (Server Storage); t10 at t10.org
Subject: Re: SAS-2 rev.15 Missing Sync lost message definition
It looks to me that the DWS Lost message does the same job. I can hardly see
why there is a need for two.
These are however minor problems. I have much bigger problem with the fact
that the comma characters are so sparse in the SAS protocol, resulting in a
longer time to acquire synchronization, specially in the noisy environment
(please note that with a lower bit energy in faster rates the SNR drops
dramatically), which may lead to link resets - catastrophic from the
performance point of view.
----- Original Message -----
From: "Elliott, Robert (Server Storage)" <Elliott at hp.com>
To: <t10 at t10.org>
Sent: Tuesday, December 02, 2008 11:17 AM
Subject: RE: SAS-2 rev.15 Missing Sync lost message definition
>* From the T10 Reflector (t10 at t10.org), posted by:
> * "Elliott, Robert (Server Storage)" <Elliott at hp.com>
> The SP receiver detects ALIGNs, TRAIN_DONEs, and Dwords and sends them as
> ALIGN Received, TRAIN_DONE Received, and Dword Received messages. See
> figure 35 on page 72.
> If dword synchronization has been lost, however, it stops sending those
> messages. SP_DWS tells the SP receiver that dword synchronization has
> been lost using the Sync Lost message. See this wording on page 285:
> "The ALIGN Received, Dword Received, and TRAIN_DONE Received messages are
> only sent after the SP_DWS state machine has achieved dword
> From: owner-t10 at t10.org [mailto:owner-t10 at t10.org] On Behalf Of Samek
> Sent: Thursday, November 27, 2008 1:46 PM
> To: t10 at t10.org
> Subject: SAS-2 rev.15 Missing Sync lost message definition
> SP_DWS (6.9) defines a Sync Lost message sent by the SP_DWS state machine
> to the SP receiver, however there is no definition anywhere what the SP
> receiver should do with this message. Any suggestions?
> Happy Thanksgiving
> Samek Mokryn
> Halstor Inc.
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