Petar,
My
concern about the 100m OM3 reach is not with access layer switch to server
connections, which are shorter with higher density servers, but with backbone
connectivity (switch-to-switch connectivity).
Conversion
to high density servers doesn’t affect distances from the switches located in
Main Distribution Area / Main Distributor (the core of the data center
infrastructure) to the switches located in the Horizontal Distribution Area /
Zone Distributor (commonly one per row). These distances are affected only by
the physical dimensions of a data center and location of the Main Distribution
Area / Main Distributor, which is hopefully, but not always near the physical
center of the data center.
Regards,
Jonathan
From: Petar Pepeljugoski
[mailto:petarp@US.IBM.COM]
Sent: Friday, March 14, 2008 7:09 PM
To: STDS-802-3-HSSG@LISTSERV.IEEE.ORG
Subject: Re: [802.3BA] Longer OM3 Reach Objective
Hello Jonathan,
While I am
sympathetic with your view of the objectives, I disagree and oppose changing
the current reach objective of 100m over OM3 fiber.
From my
previous standards experience, I believe that all the difficulties arise in the
last 0.5 dB or 1dB of the power budget (as well as jitter budget). It is
worthwhile to ask module vendors how much would their yield improve if they are
given 0.5 or 1 dB. It is responsible for most yield hits, making products much
more expensive.
I believe that
selecting specifications that penalize 95% of the customers to benefit 5% is a
wrong design point.
You make
another point - that larger data centers have higher bandwidth needs. While it
is true that the bandwidth needs increase, you fail to mention is that the
distance needs today are less than on previous server generations, since the
processing power today is much more densely packed than before.
I believe that
100m is more than sufficient to address our customers' needs.
Sincerely.
Petar Pepeljugoski
IBM Research
P.O.Box 218 (mail)
1101 Kitchawan Road, Rte. 134 (shipping)
Yorktown Heights, NY 10598
e-mail: petarp@us.ibm.com
phone: (914)-945-3761
fax: (914)-945-4134
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Jonathan
Jew <jew@j-and-m.com>
03/14/2008
01:32 PM
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Please respond to
jew@j-and-m.com
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To
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STDS-802-3-HSSG@LISTSERV.IEEE.ORG
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cc
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Subject
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[802.3BA]
Longer OM3 Reach Objective
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I am a consultant with over 25 years
experience in data center
infrastructure design and data center relocations including in excess of 50
data centers totaling 2 million+ sq ft. I am currently engaged in
data
center projects for one of the two top credit card processing firms and one
of the two top computer manufacturers.
I'm concerned about the 100m OM3 reach objective, as it does not cover an
adequate number (>95%) of backbone (access-to-distribution and
distribution-to-core switch) channels for most of my clients' data centers.
Based on a review of my current and past projects, I expect that a 150m or
larger reach objective would be more suitable. It appears that some
of the
data presented by others to the task force, such as Alan Flatman's Data
Centre Link Survey supports my impression.
There is a pretty strong correlation between the size of my clients' data
centers and the early adoption of new technologies such as higher speed LAN
connectivity. It also stands to reason that larger data centers have
higher bandwidth needs, particularly at the network core.
I strongly encourage you to consider a longer OM3 reach objective than
100m.
Jonathan Jew
President
J&M Consultants, Inc
jew@j-and-m.com
co-chair BICSI data center standards committee
vice-chair TIA TR-42.6 telecom administration subcommittee
vice-chair TIA TR-42.1.1 data center working group (during development of
TIA-942)
USTAG representative to ISO/IEC JTC 1 SC25 WG3 data center standard adhoc