Re: setting up raid10 with more than 4 drives

On 5/30/07, Luke Lonergan <llonergan(at)greenplum(dot)com> wrote:
> Stripe of mirrors is preferred to mirror of stripes for the best balance of
> protection and performance.

nooo! i am not aksing raid10 vs raid01 . I am considering stripe of
mirrors only.
the question is how are more number of disks supposed to be
BEST utilized in terms of IO performance for

1. for adding more mirrored stripes OR
2. for adding more harddrives to the mirrors.

say i had 4 drives in raid10 format

D1 raid1 D2 --> MD0
D3 raid1 D4 --> MD1
MD0 raid0 MD1 --> MDF (final)

now i get 2 drives D5 and D6 the i got 2 options

1. create a new mirror
D5 raid1 D6 --> MD2
MD0 raid0 MD1 raid0 MD2 --> MDF final

OR

D1 raid1 D2 raid1 D5 --> MD0
D3 raid1 D4 raid1 D6 --> MD1
MD0 raid0 MD1 --> MDF (final)

thanks , hope my question is clear now.

Regds
mallah.

>
> In the stripe of mirrors you can lose up to half of the disks and still be
> operational. In the mirror of stripes, the most you could lose is two
> drives. The performance of the two should be similar - perhaps the seek
> performance would be different for high concurrent use in PG.
>
> - Luke
>
>
> On 5/29/07 2:14 PM, "Rajesh Kumar Mallah" <mallah(dot)rajesh(at)gmail(dot)com> wrote:
>
> > hi,
> >
> > this is not really postgresql specific, but any help is appreciated.
> > i have read more spindles the better it is for IO performance.
> >
> > suppose i have 8 drives , should a stripe (raid0) be created on
> > 2 mirrors (raid1) of 4 drives each OR should a stripe on 4 mirrors
> > of 2 drives each be created ?
> >
> > also does single channel or dual channel controllers makes lot
> > of difference in raid10 performance ?
> >
> > regds
> > mallah.
> >
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