topic about mirror disk in Operating System - HP-UX

about mirror disk

vofsky — Thu, 08 May 2003 20:08:44 GMT

Could anyone help me to resolve this problem?
After I completed the following steps ,I got an error message"there is no free disk space..."
1.pvcreate /dev/dsk/c0t0d0
2.mkdir /dev/vg01
3.mknod /dev/vg01/group c 64 0x010000
4.vgcreate vg01 /dev/dsk/c0t0d0
5.lvcreate -L 500 -n data vg01
6.lvextend -m 2 /dev/vg01/data
error message:there is no free disk space...
BTW this is a new disk (36G).
thank you

Re: about mirror disk

A. Clay Stephenson — Thu, 08 May 2003 20:16:06 GMT

With strict mirroring policy, a mirror PE's cannot exist on the same physical volume. You need to pvcreate another disk, vgextend vg01, and then do your lvextend -m 2.

Re: about mirror disk

Patrick Wallek — Thu, 08 May 2003 20:20:01 GMT

The problem here is the fact that you are trying to mirror onto the same disk and by default LVM does NOT let you do that. What you need to do is this:

# lvextend -s n -m 2 /dev/vg01/data

Why do you want 2 additional copies (3 copies total) on the same disk?

Re: about mirror disk

Michael Tully — Thu, 08 May 2003 20:30:37 GMT

The only proper way to mirror logical volumes effectively is to have to different physical volumes in which to do this, so that one goes belly up the second can be used. Purchasing additional disks are not that expensive.

Re: about mirror disk

Sunil Sharma_1 — Fri, 09 May 2003 04:14:44 GMT

Hi,

The problem is that you have only one deisk in volume group and you are tring to mirror it using
lvextend -m

so you are getting error.

Sunil

Re: about mirror disk

Paula J Frazer-Campbell — Fri, 09 May 2003 14:38:46 GMT

AS has been said you are trying to mirror to the same disk - not allowed and not reccomended.

Reasons are :-

1. If this disk failed then both sides of the mirror are lost.

2. The disk more than likley would have problems in having to write the same data to two areas on each and every write.

Paula

Re: about mirror disk

Bruce Troutman — Fri, 09 May 2003 15:11:03 GMT

by default lvm is set up with a strict mirroring policy so it won't allow the mirror on the same disk. I think you can change this but I would not consider it. Not only are you not gaining availability but you are also decreasing the performance and increasing the chance of a disk failure.
If you didn't mean to make to copies use: lvextend -m 1.....

Good Luck!