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Re: F7 software RAID docs?



On Thursday 09 August 2007 09:44, Les wrote:
> On Thu, 2007-08-09 at 09:13 -0400, Neal Becker wrote:
> > Bruno Wolff III wrote:
> > > On Sun, Aug 05, 2007 at 21:42:01 -0700,
> > >
> > >   Dave Stevens <geek uniserve com> wrote:
> > >> Hello all,
> > >>
> > >> I'm thinking about a software RAID (0)  setup for my next system
> > >> revision and am curious where this occurs in (I assume) the system
> > >> setup. Can anyone point me to documentation on this?
> > >
> > > You can do a custom disk layout during install. It isn't too hard to
> > > figure out do a raid 0 install, though choosing good values for
> > > chunking might take some guesswork.
> > >
> > > What are you going to be doing that makes you think raid 0 is
> > > desirable? For modern home machines with lots of memory, this probably
> > > isn't going to give you much of a speed up in typical use. It will make
> > > the chances of your file system being lost because of a hardware
> > > problem, about double. Raid 1 or 10 seem to be more useful for home
> > > users, than raid 0.
> >
> > No!  If the prob of failure during an interval T is pf, the prob of
> > failure for an array of 2 drives during T is 1 - (1-pf)^2.
>
> Just for completeness it should be pointed out that this is for random
> failures.  If the failure mode is non-random, say a design flaw or
> mechanical assembly error, the formula doesn't hold, and the error
> probability is nearly the same as a single disk.  Although in "real
> life", the errors are likely somewhere between random and design
> related, so the formula is very close to the actual figure, especially
> given reasonable testing standards by the manufacturer.
>
> Regards,
> Les H

not to contradict anything said here, but Seagate estimates that the MTBF for 
my drive, a 7200.10 series 320 GB SATA is 700,000 hours. Half of that is 
still 34 years. Probably the drive will be full before then...

And the backup is planned to be a separate larger drive that will mirror the 
system overnight. What do people recommend for that, rsync? Ideally the 
backup would be incremental and leave me with a drive that just needs to be 
configured as master (boot drive) to get me back in business.

Dave

-- 
The modern conservative is engaged in one of man's oldest exercises in moral 
philosophy; that is, the search for a superior moral justification for 
selfishness." - John Kenneth Galbraith


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