On Fri, Aug 03, 2001 at 04:21:51PM +1000, dkwok wrote:
> > I think RAIDframe don't support disks of different size insode the same
> > RAID, but ccd does. However, if as they're from different size you won't
> > be able to strip them, they will just get concatened.
> >
> 
> What is the difference between stripping and concatening in so far as Raid-0
> is concerned?
> 
> Mine raid disk is infact Raid10. One Raid1 set of 2@20G IDE and another
> Raid1 set of 2@15G and then they are joined together with Raid-0. What is
> the drawback with this setup? I have it working however I 'd better
> understand the downside before anything bad happened to it.

The main downside is performances problems: with stripping, data are
equally distributed across the component ("interleaved"), so when you read a
large file data are fetched from all component providing a performances boost.
Concatening will just put component one after the other (sector 0 to x are on
component 0, x to y on component 1, etc).
To see the difference, do a 'dd' from your raid0 raw device to /dev/null.
With stripping, you'll see activity on all component. With concatenation
you'll see activity on the first component, then the second, etc ...

--
Manuel Bouyer <bouyer@antioche.eu.org>
--