Serial Port Concentrators vs. KVMs

Dan Kidger daniel.kidger at
Thu Apr 24 11:28:12 EDT 2003

> >     Having used both KVMs and serial port concentrators, I have my own
> > opinions about the advantages and disadvantes of each.  I was hoping
> > that list members might share their opinions as well.

Traditionaly we have used serial lines for all large clusters, often with a
small say 4 or 8-way KVM.
The KVM gives us access to the management node(s) (and various hence X11
based tools), other servers (e.g raid controllers, QsNet switches), together
with a spare connection or two. The spare connections are used only when we
have odd 'problem nodes' or when setting the BIOS to serial for the first

IMHO Linux based serial line concentrators like Cyclades et al. are
particularly easy to setup and maintain

However the current trend is for all new rack-mount nodes to offer some sort
of BMC (baseboard management controller) with an ethernet connection. As
well as giving remote power cycling, this should allow 'Serial_over_Lan" -
the headnode in the cluster acts as a server and you can telnet/ssh to it on
a certain port and hence reach the console on any compute node. As a result,
our latest cluster we have got has neither a KVM nor a serial port


Dr. Dan Kidger, Quadrics Ltd.      daniel.kidger at
One Bridewell St., Bristol, BS1 2AA, UK         0117 915 5505
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