Date: Fri, 6 Dec 2002 16:40:37 +0000 From: Matthew Seaman <m.seaman@infracaninophile.co.uk> To: freebsd-questions@FreeBSD.ORG Subject: Re: clarification of man dump Message-ID: <20021206164037.GB1630@happy-idiot-talk.infracaninophi> In-Reply-To: <20021206154739.GB69019@grummit.biaix.org> References: <20021206154739.GB69019@grummit.biaix.org>
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On Fri, Dec 06, 2002 at 04:47:39PM +0100, Joan Picanyol i Puig wrote:
> Hi,
>
> I have some trouble understanding the last part of 'man dump', from "An
> efficient method of...". My understanding is that the example means:
>
> 1. Take a level 0 dump once a month
> 2. Take a level 1 dump once a week
> 3. Take a level 3 dump on mondays, a level 2 on tuesdays, a level 5 on
> wednesdays and so on until a level 9 on sundays.
>
> Am I missing something? What's so "efficient" from doing it this way
> (why)?
It's a compromise between minimising the number of tapes required to
restore the system to the state it was in on any particular date ---
clearly just taking a level 0 dump every day means you only have to
restore from one tape set --- and getting the most data possible onto
a limited number of backup tapes --- best economy is achieved by doing
a full level 0 backup once, and then each day just doing an
incremental backup of what changed since the previous day: however
leave too long between level 0 dumps and you're likely going to have a
real chore wading through a mountain of tapes to get back to any
particular state.
Cheers,
Matthew
--
Dr Matthew J Seaman MA, D.Phil. 26 The Paddocks
Savill Way
Marlow
Tel: +44 1628 476614 Bucks., SL7 1TH UK
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