topic Re: Confusd with LVM commands and arraycfg command. in Disk Enclosures

Confusd with LVM commands and arraycfg command.

Larry Salard — Thu, 23 Dec 2004 03:26:43 GMT

I'm planning a Oracle 9i RAC install on HP-UX 9000 Series800, two node configuration, which HP AutoRaid 12H as shared storage.

But i was confused by the HP mannual and Oracle's Step by step install instruction.

In HP commands manual:
When creating LUN on disk array, use "arraycfg", but that command limit you with only 8 LUN per array.

While in Oracle's Step by step guide, it use the following command sequence (also on a disk array):
pvcreate -f /dev/rdsk/c0t12d0
mkdir /dev/vg_ops
mknod /dev/vg_ops/group c 64 0x060000
vgcreate /dev/vg_ops /dev/dsk/c0t12d0
vgchange -a y vg_ops

then following with a lot of lvcreate commands:
lvcreate -n P901_control_01.ctl -L 110 /dev/vg_ops...

in this way, it can create at maxium 255 logical volume on a disk array.

So, which one is correct?!

Re: Confusd with LVM commands and arraycfg command.

Bernhard Mueller — Thu, 23 Dec 2004 04:52:45 GMT

Larry,

both are correct.

you should not confuse LUNs (logical drives on the array) with LVM logical volumes (lvols).

The 12H lets you create 8 LUNs.
run
ioscan -fnCdisk
to see the HW path
run
insf -e
to create device files like /dev/dsk/c#t#d0 (LUN0) ..d1 (LUN1) etc. for those HW path.

the LUNs are like disks (if you did not have an array but a JBOD with individual disks.

So from here on the rest is LVM:
run
pvcreate /dev/rdsk/c#t#d0
to create an LVM header on the LUN
mkdir /dev/vg....
etc etc.

Regards,
Bernhard

Re: Confusd with LVM commands and arraycfg command.

Bernhard Mueller — Thu, 23 Dec 2004 04:58:03 GMT

Larry

one additional hint: Use SAM to create new LUNs on the 12H, this is the easiest way and it will also create device files as necessary. If I remember correctly SAM would also show you how much space remains allocatable on the 12H for additional LUNs. But note that for perfomance it is better not to fully use the available space.

Regards,
Bernhard

Re: Confusd with LVM commands and arraycfg command.

Patrick Wallek — Thu, 23 Dec 2004 11:39:58 GMT

If you want the best performance from your AutoRaid 12H allocate only 1/2 (half) of the available disk space to LUNs in the array. Thhis will allow you to keep all data in RAID 0+1. If you allocate more than 1/2 of the space to LUNs then some of your data will be forced into RAID 5 which will not perform as well.

Re: Confusd with LVM commands and arraycfg command.

Larry Salard — Thu, 23 Dec 2004 22:39:57 GMT

Great! Thank you Bernhard Mueller and Patrick Wallek :)

Regards
Larry