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about mirror disk

 
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vofsky
Frequent Advisor

about mirror disk

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

6 REPLIES 6
A. Clay Stephenson
Acclaimed Contributor
Solution

Re: about mirror disk

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.
If it ain't broke, I can fix that.
Patrick Wallek
Honored Contributor

Re: about mirror disk

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?
Michael Tully
Honored Contributor

Re: about mirror disk

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.
Anyone for a Mutiny ?
Sunil Sharma_1
Honored Contributor

Re: about mirror disk

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
*** Dream as if you'll live forever. Live as if you'll die today ***
Paula J Frazer-Campbell
Honored Contributor

Re: about mirror disk

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
If you can spell SysAdmin then you is one - anon
Bruce Troutman
Advisor

Re: about mirror disk

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!