Originally posted by: ManuelSCC

Hi,

A client has just received a new POWER6 520, with 4 internal SAS disks (140 GB each).
The server came already installed (AIX 5.3), with rootvg on hdisk0, and hdisk1, hdisk2 and hdisk3 not assigned to any VG.

They don't want to mirror rootvg, because they don't want to use two 140 GB disks just for rootvg, so tey've decided to make an array (raid 5) with the 4 disks, and leave rootvg on this array, and use rootvg for OS, applications and data.

What they've done is:

• change hdisk1, hdisk2 and hdisk3 to array candidates. This created pdisk0, pdisk1 and pdisk2 and deleted hdisk1, hdisk2 and hdisk3.
• create a raid 5 array with pdisk0, pdisk1 and pdisk2. This created hdisk1 (about 266 GB).
• mirror rootvg from hdisk0 to hdisk1.
• break the mirror and remove hdisk0 from rootvg
• change hdisk0 to array candidate. This deleted hdisk0 and created pdisk3.
• add pdisk3 to the hdisk1 array.

Now, if we go to smit devices menus, we see that hdisk1 is a 4 disk raid 5 array, but AIX still sees it as a 266 GB hdisk.
Is there a way to tell AIX that hdisk1 has increased?
I've seen that chvg -g does not for rootvg.
If there's no other option, we're thinking about reinstalling AIX, but I'm not sure that the installation will recognize the 4 disks as an array, and not as individual hdisks.

Does anybody know something about this?

Thanks.
#AIX-Forum

Originally posted by: kappa

Funny, isn't it?

At first, the client did not want 2x 140GB in rootvg.
Now, he is using 4x 140GB in rootvg, 1x 140GB just for parity data.

The client want to use fast disk access,
but RAID5 imposes a 4 disk penalty for each write I/O op.
Local RAID5 - for a boot/system disk!

The client wants to move data around, wants to reorganize its RAID5,
just to keep the preinstalled AIX Test alive!
Stupid, everyone would install a fresh AIX or clone with a Install Image.

I would not want to know if I can re-organize the RAID5.
It's an academic question - a silly one!
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