Date: Wed, 25 Jul 2001 07:51:58 +0200 From: "Steve O'Hara-Smith" <steveo@eircom.net> To: Wilko Bulte <wkb@freebie.xs4all.nl> Cc: jkh@FreeBSD.ORG, mike@adept.org, jandrese@mitre.org, geniusj@bluenugget.net, mike@sentex.net, sucho2@quasar.phys.vt.edu, mwm@mired.org, freebsd-stable@FreeBSD.ORG Subject: Re: Regarding hw.ata.wc="1"...... Message-ID: <20010725075158.0e5df923.steveo@eircom.net> In-Reply-To: <20010724220400.A1558@freebie.xs4all.nl> References: <3B5D94E7.4680ACEF@mitre.org> <Pine.BSF.4.21.0107240845420.92951-100000@snafu.adept.org> <20010724093512W.jkh@freebsd.org> <20010724204131.355a3ae6.steveo@eircom.net> <20010724220400.A1558@freebie.xs4all.nl>
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On Tue, 24 Jul 2001 22:04:00 +0200
Wilko Bulte <wkb@freebie.xs4all.nl> wrote:
WB> > favour of a complete spare system and use a software mirror (or load
WB> > duplication) to keep it available for a hot swap. One benefit of this approach
WB> > is that the hardware is on *much* shorter lead times this way because it's all
WB> > off the shelf and alternatives are feasible.
WB>
WB> But lots more downtime if you are unlucky. Like you said, it all depends on
You only get downtime if you lose *both* systems in the time it takes
to fix a breakage. Higher levels of redundancy are of course trivial.
WB> > There's more than one way to skin a cat.
WB>
WB> You should not talk about skinning cats in Jordan's presence.
Ooops, sorry Jordan.
... Two replies in one this is OT after all ...
MM> one system crashing. What's in the intersection are things that shut
MM> down the power to the active machine but not the hot spare, which are
MM> normally pretty rare. Parallel power sources will make them more
MM> common, but that's a more expensive proposition than just keeping a
Two small UPSs is not a major expense, and will ensure enough PSU
reliability that you don't lose *both* machines without at least one completing
a shutdown unless you get multiple UPS failures. If there are two phases in
the building use them to reduce the probability of simultaneous mains failure
too.
--
Directable Mirrors - A Better Way To Focus The Sun
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