8 Disks on One Channel is bad?

[Laurie_2]

Hi All,

We have a K360 HP-UX 11.0 with
8 disks (SEAGATES) on one channel. I am told this is very bad and that buying more
memory and another CPU will not fix this bottle neck and that we need to put some of these disks on another channel.

We are using GSC Fast/Wide SCSI interfaces.

On the back of our box we have:

CORE I/O = F/W Diff going disk

Left CORE I/O = HP-PB 16 Bit
Diff. that is
Terminated.

I am told we can use either
another HP-PB Card or an HSC
Card to create another channel.

I assume I can use the HP-PB
card that is terminated to create another channel.

Do I just hook up the cables?
Or do I need to do a bunch of
vgexports and vgimports?

I need some sort of instructions. We have an
Informix Database and when I do SAM logical Vol. display
all the informix disks show
"Unused"..I quess that's OK.

TIA,
Laurie

[S.K. Chan]

You should be able to just connect to the other channel (the HP-PB card) and upon bootup, ioconfig will create another set of device files (alternate or redundancy device paths) which then you can use by vgextending your existing VGs. Eg:
# vgextend vg01 /dev/dsk/cXtXdX
# vgdisplay -v vg01
==> Check if the "alternate" path is defined.

As for the other q, yes SAM will report "unused" for a raw LV. Until HP comes up with a fix for this, what you can do is mark that device yourself in SAM as "used" to avoid and confusion.

Disks and File Systems->Action->Mark LV As Used...

[A. Clay Stephenson · Accepted solution]

Hi Laurie:

The older configuration guides give these guidelines for a single FWD SCSI bus:

Heavy Sequential I/O 5 Disks
Heavy Random I/O 10 Disks
Light I/O 15 Disks

The sustained throughput for an HP-PB SCSI FWD Card is 7-10MB/s and for an HSC FWD SCSI Card is 12-15MB/s. You have to install an IO Card that has additional slots to add another HSC controller but these are cheap on the used market. As to how to move disks that becomes difficult without knowing more. If you Informix is using true raw disk I/O (e.g. /dev/rdsk/c1t4d0 e.g) then you have some database work to do first. If you are using LVM raw I/O (/dev/vg01/rvlvol3 e.g.) then it's much easier. You can do a vgexport and then vgimport using the new paths.