Re: [PATCH 009 of 11] md: Support stripe/offset mode in raid10

Neil Brown
2006-05-03T00:06:12Z

On Tuesday May 2, a1426z@gawab.com wrote:
> NeilBrown wrote:
> > The "industry standard" DDF format allows for a stripe/offset layout
> > where data is duplicated on different stripes. e.g.
> >
> > A B C D
> > D A B C
> > E F G H
> > H E F G
> >
> > (columns are drives, rows are stripes, LETTERS are chunks of data).
>
> Presumably, this is the case for --layout=f2 ?

Almost. mdadm doesn't support this layout yet.
'f2' is a similar layout, but the offset stripes are a lot further
down the drives.
It will possibly be called 'o2' or 'offset2'.

> If so, would --layout=f4 result in a 4-mirror/striped array?

o4 on a 4 drive array would be

A B C D
D A B C
C D A B
B C D A
E F G H
....

>
> Also, would it be possible to have a staged write-back mechanism across
> multiple stripes?

What exactly would that mean? And what would be the advantage?

NeilBrown