RS/6000 - SUPERSIZING MY HARD DRIVES

[in...@lalift.com]

Hey

I am running an older RS6000 running 4.2.1.

We want to buy some increased storage from IBM for our RS/6000 which
is running AIX 4.2.1. It is currently configured as a 9G SCSI Primary
with RAID5 across three 4.5G SCSI drives. These are also mirrored, for
a total of 8 drives.

I would want to keep the same raid and mirroring layout, but go up to
72G primary with three 36G raid drives and mirrored, to ensure we
would have enough space.

Is there a way that I can add drives that are larger on one side of
the mirrored setup, and then have it sync the files over to the new
drives, and then replace the other drives?

If you can point me to a link with some headstart on the procedure
that would be great.

Thanks, Jeff

[steven_nospam at Yahoo! Canada]

If I read you correctly, you are set up something like this?

ROOTVG
hdisk0 (9gb) <-------> hdisk1 (9gb)

RAIDVG
hdisk2 (9gb) <-------> hdisk3 (9gb)
pdisk0 (4.5gb) pdisk3 (4.5gb)
pdisk1 (4.5gb) pdisk4 (4.5gb)
pdisk2 (4.5gb) pdisk5 (4.5gb)

You have a few considerations:

1) Will the newer larger disks that you purchase operate on my older
RS/6000 and under AIX 4.2.1?

I thought I heard somewhere that the latest 36GB or 72GB model drives
that they are making would require both a firmware and O/S upgrade.
However, you should be able to confirm this with IBM in their
configurator or with your rep...

2) Whenever mirroring a disk, you can generally mirror a small disk to
a larger one, you just can't do the opposite. (In other words, you can
mirror data from a 9GB to a 36GB no problem, just don't try 36GB onto a
9GB!

3) It seems like an awful waste to use RAID5 with only three disks
since you lose 33% of your storage for parity. Also, you are using
RAID5 to prevent against any single disk dying, but then you also
mirror?? (essentially mirroring the parity). Why not just use these
disks in a SAME setup (stripe and mirror everything) with RAID1 or
RAID1+0?

Your method:

Total non-primary storage: 216 GB (6 X 36gb)
Less mirror portion: - 108 GB
Less RAID5 parity area: - 36 GB
===========
72 GB

Using SAME method:

Total non-primary storage: 216 GB
Less mirror portion: - 108 GB
===========
108 GB

Anyway, this is a bit off your topic. I just use the commands in "smit
devices" and "smit lvm" to create my mirrors, VGs, and LVs.