geom - help ...

[R. B. Riddick]

--- Matthew Seaman <m.seaman at infracaninophile.co.uk> wrote:
> Marc G. Fournier wrote:
> > 
> > So, again, if I'm reading through things correctly, I'll have to do
> > something like:
> > 
> > gstripe st1 da1 da2
> > gstripe st2 da3 da4
> > gmirror drive st1 st2
> > newfs drive
> 
> That's the wrong way round, I think.  If you lose a drive, then you've
> the whole of one of your stripes and have no resilience.  Shouldn't you
> rather stripe the mirrors:
> 
>    gmirror gm0 da1 da2
>    gmirror gm1 da3 da4
>    gstripe gs0 gm0 gm1
>    newfs gs0
> 
> This way if you lose a drive then only one of your gmirrors loses
> resilience and the other half of your disk space is unaffected.
> 
Yup!
In the case
  M(S(a,b),S(c,d))
the content
  on 'a' and 'c'
and
  on 'b' and 'd'
would be identical, so that the u had to do it handish and efficient or
automatically and inefficient in case of a disk failure.

I personally put the boot-stuff on a gmirror (no striping).
So u might want to use something like this:
  M(a1,c1) for /
  S(b1,d1) for /not-so-important
  S(M(a2,c2),M(b2,d2)) for /usr/home

By the way: A correct syntax would be
  gmirror label -b load gm0 da1s1a da3s1a
  gmirror label -b load gm1 da1s2d da3s2d
  gmirror label -b load gm2 da2s2d da4s2d
  gstripe label -s 65536 gs0 da2s1d da4s1d
  gstripe label -s 65536 gs1 mirror/gm1 mirror/gm2

Oh! And I am experimenting with my geom_raid5 implementation... But it is quite
slow in write to UFS (but non-concurrrent write to raw-device is quite fast
already). U can download it here (but it is quite difficult to integrate - many
files have to be changed handish):
  http://home.tiscali.de/cmdr_faako/geom_raid5.tbz
:-)

-A

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