Re: Four Drive RAID-5 on RAIDFrame Considered Harmful...

2007/10/10, Robert P. Thille <[email protected]>:
>
> On Oct 9, 2007, at 6:53 PM, Thor Lancelot Simon wrote:
>
> > On Tue, Oct 09, 2007 at 04:59:58PM -0700, Robert P. Thille wrote:
> >>
> >> I tracked it down to the problem that 2 and 3 are relatively
> >> prime :-)
> >> Given 4 drives in a RAID-5 setup, you get 3 data blocks per raid
> >> stripe,
> >> but the filesystem block size Must be a power of 2, so you always
> >> have
> >> to write at least one partial stripe.
> >
> > No.  Examine the "maxcontig" FFS parameter.
> >
>
> maxcontig appears to be obsolete.  Looking thru the sources (current
> from a month or so ago), I don't think it's used by the kernel/
> filesystem, and the options mentioned in postings I found in the
> mailing lists don't seem to exist anymore.
>
> Am I missing something?
>
> Thanks,
>
> Robert
>
>
> --
> Robert Thille                7575 Meadowlark Dr.; Sebastopol, CA 95472
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>

I wouldn't recommend RAID 5 at all. If one of your drives die or your
controller dies (in the case you would have hardware raid), you can
have a lot of trouble recovering your data. But if you have 1x RAID 0
plus RAID 1 (RAID 10 ?)  you can always replace the drives and copy
the data since the data is always available as a whole unit.

Zafer.