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Date:      Sat, 22 Jan 2005 05:56:18 +1100
From:      Peter Jeremy <PeterJeremy@optushome.com.au>
To:        Kevin Oberman <oberman@es.net>
Cc:        freebsd-stable@freebsd.org
Subject:   Re: Disabling write-behind on IDE drives, and SMART
Message-ID:  <20050121185618.GD68808@cirb503493.alcatel.com.au>
In-Reply-To: <20050121172837.2F80A5D08@ptavv.es.net>
References:  <20050121164928.GA50279@falcon.midgard.homeip.net> <20050121172837.2F80A5D08@ptavv.es.net>

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On Fri, 2005-Jan-21 09:28:37 -0800, Kevin Oberman wrote:
>10 minutes (or even 1 minute) would be fine IF you have the system
>shutdown when the main power fails, but if the system is unattended and
>active and power goes out, it will simply keep going until the UPS dies
>and will still leave your disk in a bad state.
>
>The right answer is to run nut or other UPS monitor to shutdown the
>system when power fails.

Agreed.  ACPI helps enormously here.  When implementing this, remember
to ensure that things recover when mains power is restored in the
interval between when the UPS says "I'm about to die, shutdown now"
and when it actually dies.

> Or, better still, have generator backed power
>with about an hour of UPS to give the generator time to get up to speed
>and on-line.

Huh?  Most generators take a lot less than an hour to get going.  15-30
seconds would be a typical value.  If your backup generator takes an
hour to start, it is probably overdue for servicing :-).

> But that is still less than perfect. Generators fail, are
>often not tested regularly, and will eventually run out of fuel.

If this is important to you then it needs to be covered as part of
your business continuity or disaster recovery plan.

-- 
Peter Jeremy



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