From: cassidy@esd55.enet.dec.com (Charlie Cassidy)
Newsgroups: comp.arch.storage
Subject: Re: Query: Solid State SCSI Systems
Date: 10 Nov 92 21:52:00 GMT
Article-I.D.: nntpd.1992Nov10.215200.2665
Reply-To: cassidy@memory.enet.dec.com
Organization: Digital Equipment Corporation


In article <1992Nov10.021022.14711@news.arc.nasa.gov>,
lamaster@pioneer.arc.nasa.gov (Hugh LaMaster) writes:

|>In article <1992Nov9.203919.9793@nntpd.lkg.dec.com>,
|>cassidy@esd55.enet.dec.com (Charlie Cassidy) writes:
|>|> 
|>|> We are showing the following products at COMDEX next week.  We also
|>|> announced today the EF5x family of DSSI SSDs for Digital's VAX and ALPHA AXP 
|>|> systems.  Please contact me or visit us at the Digital's OEM booth
|>on the Comdex
|>
|>
|>I guess this seems like an excessively "Commercial" posting for
|>this newsgroup.  I think it belongs on biz.dec.announce, or
|>comp.newprod, etc.  Since it is here, however, I have a few
|>questions:
|>

Sorry about the commercial.  It was easier to grab the text file that
the marketing folks had handy than to retype in the details.  I wouldn't have
done it except that it was an answer to the query.  At least I didn't post the 
press release :-).

I'll answer the questions as best I can - but realize that the SCSI firmware is
still being worked on (we did the DSSI FW first).  In some cases, I'll give the
answer for the DSSI version if it makes sense.

|>
|>What is the transfer rate?  May I assume that it is 10MB/sec?

Peak rate over the wire is 10 MB/s.  Sustainable data rate will be less.  
Theoretical max sustained (based on the HW design) is about 5 MB/s -
limited by the error correction engine.  It'll be less than that - probably 
about 2-3 MB/s.  The EF51R does 2 MB/s sustained over DSSI.  

|>What is the measured latency through a real SCSI-2 controller?
|>
|>For example, what is the latency I can expect on a DECsystem 5500?
|>
TBD - should have an answer in late January.  On DSSI, we've measured 4 ms at 
the application level - which includes QIO processing, driver overhead (both
disk and DSSI port), device access, data transfer and I/O post processing (both
interrupt and fork level).

|>Measured the way DEC usually measures these things, how many QIO's/sec
|>can the device handle at the usual delay points?  Can the existing
|>controllers, such as the one on the DECsystem 5500, saturate it?
|>
TBD - The EF51R does about 850 QIO/s on a VAX 4000-600 through the
embedded DSSI adapter, which is rated at 1200 QIO/s.  I would expect similar 
throughput for the ESP510 through a decent SCSI-2 adapter.  We've got a 
DECsystem 5500 in the lab as one of the systems we'll use to initially debug
the firmware, so I should have an exact number in late January.

--
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"Good things can happen, and frequently do, to people as brainy and footsy
as you." - Dr. Seuss
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Charlie Cassidy                        Internet: cassidy@memory.enet.dec.com
Digital Equipment Corporation          Amateur Radio: charlie@n1hlr.ampr.org
Memory Products Group - SHR1-4/O11
333 South Street                       This posting reflects the opinion of 
Shrewsbury, MA 01545                   the author, not Digital Equipment Corp
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Newsgroups: comp.arch.storage