Raid 5 on a Rack Mount Dual 1ghz power pc G4?

[Atro Tossavainen]

Nick,

> New to getting Linux going on the mac hardware. We would like to use the
> rackmount G4 as a file server running Linux.
> We have got a test version YDL going, and learnt some about video modes in
> the process.
> What we would like to do is a raid 5, I have a sneaky suspicion that the G4
> won't raid 5 even under OS 10.2.6. Any suggecstions or links gratefully rec
> so we can read up on the topic.

The hardware RAID features of the Promise RAID controllers on the
Xserve are not available at all on the Xserve.

I can't tell you what kind of software RAID OS X will allow you to do
as I never booted our Xserve to OS X.

Linux will allow you to RAID0, RAID1, RAID5 in software.  We have a
Xserve with dual disks where the /boot and / partitions are mirrored
on both disks and /scratch is a striped volume across the remaining
space on them.

On x86, the Linux kernel would recognize RAID partitions at bootup based
on the disk partition type flag 0xfd ("Linux raid autodetect"). On PPC,
you can't do this because of the different partitioning scheme, and as
a result, if you want to boot from a metadevice, you need to create an
initial RAM disk for booting that sets up the necessary RAID components,
mounts your root filesystem, then changes root to the RAID root
filesystem and starts init.  I've got this done and you can have it
if you need it.

A rather unfortunate side effect of this kludge is that it's vulnerable
to changes in the kernel.  The 2.4.21 kernel changed something in the
way the Promise controller support works.  The hdX drive letters
changed, but not only that, I am also unable to access the second drive
at all, can't start RAID, can't mount root, so I'm staying at 2.4.20
for the time being.  I've tried to work this out with Ben H. but
haven't gotten anywhere so far.

-- 
Atro Tossavainen (Mr.)               / The Institute of Biotechnology at
Systems Analyst, Techno-Amish &     / the University of Helsinki, Finland,
+358-9-19158939  UNIX Dinosaur     / employs me, but my opinions are my own.
< URL : http : / / www . helsinki . fi / %7E atossava / >

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