Distributed LV under SG

[RAC_1]

Background -
SG(A.01.02) between two superdome.
packages-2
package1-vg01,vg02 and vg03 with 1 LV in each VG.
package 2-vg09-one LV.

(ALL coming from VA7400-raid 0+1)

Problem
high disk ios for all volume groups. Some disks in all VGS hitting high while some are not. (high read/write ios for some disks while for others it is not high)

lv's created without -D and -s g)

1 My question is -- If raid is at 0+1, what performance improvement is going to happen if I recreate lvs with -D -s g?

2 Also we keep on extedning these lvs to accomdate additional space requiremets.

3 What effect -D -s g will have when extending lvs.
(we have Online JFS-advanced)

4 Is there any connection between distributed LVs(-D -s g)and SG.

[RAC_1]

no replies.

pushing to the top

[John Palmer]

Hi,

1. You will spread I/O's more evenly across 'disks' at the LVM level but as these are mirrored and striped in the VA7400 then I don't see any benefit.

2/3. Not a problem whether you use -D + -s g or not.

4. No

Generally, you'll be better off investigating and fixing why your apps are doing so much I/O (e.g. badly written SQL etc) rather than trying to get a small increase in performance from the underlying hardware.

Regards,
John