Re: [linux-lvm] LVM and fault tolerance

[Anders Widman <andewid@tnonline.net>]

Is it possible to have more than 5 disks in a raid-5 array?

Russell Coker wrote:

> On Friday 23 March 2001 10:59, Anders Widman wrote:
> > > For example, you can create a number of md devices, using RAID1 or RAID5
> > > for fault tolerance, and then run pvcreate on them and manage them with
> > > lvm.
> > >
> > > I'm doing this right now with a 4-disk RAID5 array (3 disks + 1 hot
> > > spare), and it seems to be working just fine.
> >
> > So, how is this actually working then. Let say I have this disk
> > configuration:
> >
> > 2x 40gb
> > 2x 60gb
> > 2x 80gb
> >
> > I want maximum amount of diskspace available for storage. High speed is not
> > needed at all as this is mainly for storage and streaming low bitrate
> > media. Still, I need to be able to add additional disks, maybe two extra
> > 80gb disks. Would it be possible to keep ecc/crc data on one disk only, or
> > stripe it over all disks. Mirroring is to expensive in this sence too.
> >
> > The problem with RAID-5 is that all disks need to be of the same size and
> > that it is not expandable (or is it?).
>
> Create a 40G partition on each disk and run RAID-5 over them for 200G of
> redundant storage.
> Then create a 20G partition on each 60G and 80G disk and make a RAID-5 on
> them for 60G of redundant storage.
> Then create another 20G partition on each 80G disk and run RAID-1 on them for
> 20G of redundant storage.
>
> That gives 280G of RAID storage.  But having 2*RAID-5 and one RAID-1 set on
> the same 80G disks won't be good for performance.
>
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