Doug
I realize that your 10b8b arithmetic was probably meant to be approximate,
but I'd still like to point out that 10G Ethernet technology uses the 8b
number when quoting bandwidth whereas e.g. IB quotes the 10b number (let's
refer to this as data rate vs. signaling rate).
For example: so called 10Gbps IB has a data rate limit of 8Gbps, whereas
10GE has a data rate lmit of 10Gbps (countinting TCP/IP headers as part of
the BW).
For CX-4 copper cable (Infiiniband connectors and cable) the rate of the
serdes used are actually different for the two technologies with IB having 4
lanes at 2.5GHz whereas 10G Ethernet has 4 lanes at 3.125GHz, leading again
to 8Gbps IB vs. 10Gbps Ethernet data rate bandwidth.
Regards,
Asgeir Eiriksson
Chelsio Communications Inc.
From: Douglas Gilbert <dougg@xxxxxxxxxx>
Reply-To: dougg@xxxxxxxxxx
To: Mirko Benz <mirko.benz@xxxxxx>
CC: linux-scsi@xxxxxxxxxxxxxxx
Subject: Re: SATA on mptsas performance
Date: Tue, 28 Feb 2006 22:30:16 -0500
...
BTW since SAS uses "10b8b" encoding (as do IB,
FC, SATA, PCIe, 10 gigabit ethernet on copper, etc) which
encodes 8 data bits into 10 bits on the wire then one
can flip between "<n> MB/sec" and "(<n> * 10) Mb/sec". The
capitalization (or not) of the "B" is obviously significant.
Perhaps somebody from a SAS vendor company could tell us how
much data one can really send down a 3 Gb/sec SAS/STP
connection under optimum conditions.
Doug Gilbert
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