John Eells wrote:
Skip wrote:
I have heard that the FICON Express4 4-port adapters which operate at
4Gbps speeds become slower/degraded with each channel added to the
card. That if I fill the 4 ports I may be as slow as 1/4 the rated
speed. Has anyone else heard or read about this? Is it true?
I asked our local expert about this. Her response:
[...]
In fact the response does not respond to the questions asked <g>
I vaguely remember some IBM statement about 4gbps cards. Indeed, when
more ports on the cards, already connected ports could have degraded
performance. However it is definitely NOT 1/4 of the speed, and strongly
depends on the utilizationa as well as concurrency of the utilization
peaks.
To simplify, when you connect one port on the card you can get some
maximum, MAX. No performance degradation after connecting second port,
(i don't know about third), slight performance degradation when fourth
port is connected. So *concurrent* maximum on each port could be, for
example 0.87*MAX. Or card total bandwith is 4*MAX, but 3.5*MAX.
Last but not least: CU on the other end of FICON channel is not always
able (or rather very seldom) to fully utilize 4gbps FICON. So, I
wouldn't afraid about the problem above.
My $0.02
--
Radoslaw Skorupka
Lodz, Poland
--
BRE Bank SA
ul. Senatorska 18
00-950 Warszawa
www.brebank.pl
Sd Rejonowy dla m. st. Warszawy
XII Wydzia Gospodarczy Krajowego Rejestru Sdowego,
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NIP: 526-021-50-88
Wedug stanu na dzie 01.01.2008 r. kapita zakadowy BRE Banku SA wynosi
118.642.672 zote i zosta w caoci wpacony.
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