Mirror on logical volume striped

[gigiz]

Hallo,
I have a :
1 vg with 41 disk
2 logical volume striped on 41 disk
I want know if is it possible add 41 disk and mirror it on this 2 logical volume?
If is it posssible in the mirror i lose the striping?
In attache a part of my lvdisplay and vgdisplay ...

[Shahul]

Yes, You can add 41 disks and mirror your volumes with out loosing stripes. You need to mirror by using PVG strict policy.

You will get more info in man page of lvextend or lvcreate.

Best of luck
Shahul

[Steve Lewis]

Not possible if you used lvcreate -I -i within LVM. You cannot LVM mirror that type of logical volume.

If you use full VXVM then it is possible in the volume manager.

If you create a PVG then use distributed allocation, you can mirror in LVM, but the stripes are WIDE, as wide as your VG PE size. This is too wide for sequential operations, but may be OK for equally distributed random access.

I personally think that a 41 way stripe is too many.

If you have an RDBMS on top of a striped logical volume which has its own mirroring functionality, then you may be able to use that instead, but performance will not be as good as volume manager mirroring.

If its LVM, then you may not be able to add another 41 disks to your VG, check the limits of your VG especially MAX PV, which may be set to 41.

[gigiz]

i have attached my lvdisplay and my vgdisplay
I can't create a new logical volume,
i want to mirror a logical volume already striped.
how i see if it was created whit - lvcreate -I -i within LVM ?
Why i can't mirror this logical volume
If i can mirror what is the procedure ...

[RAC_1]

You lvol is created with -i and -I options. You can mirror. Strippped lvols with -D -g can be mirrored.

[gigiz]

Are you sure ?
look it :
http://forums1.itrc.hp.com/service/forums/questionanswer.do?threadId=502310

and what is the command ?

[Steve Lewis · Accepted solution]

OK, I looked at your lvdisplay and vgdisplay from LVM.

As I suspected, you cannot add any more PVs to the VG because you are already at your limit.

Secondly, your logical volume (lvdisplay output) shows it is striped allocation with 1Mb extents, so you cannot mirror it.

If you really want to mirror this logical volume, then you must do so at the hardware/ disk array level (best option).

Otherwise, you would have to back up your data, completely re-create the volume group from scratch and restore the data from the backup.

[gigiz]

Excuse me Steve,
but your suspect is wrong . My PV limit is 255 ...
look :

--- Volume groups ---
VG Name /dev/vgdata
VG Write Access read/write
VG Status available, exclusive
Max LV 255
Cur LV 1
Open LV 1
Max PV 255
Cur PV 32
Act PV 32
Max PE per PV 9000
VGDA 64
PE Size (Mbytes) 32
Total PE 69024
Alloc PE 69024
Free PE 0
Total PVG 0
Total Spare PVs 0
Total Spare PVs in use

[Steve Lewis]

Thats not what you showed in your first posting:

--- Volume groups ---
VG Name /dev/vgdb
VG Write Access read/write
VG Status available, exclusive
Max LV 255
Cur LV 2
Open LV 2
Max PV 41
Cur PV 41
Act PV 41
Max PE per PV 17263
VGDA 82
PE Size (Mbytes) 32
Total PE 88437
Alloc PE 81672
Free PE 6765
Total PVG 1
Total Spare PVs 0
Total Spare PVs in use 0

I answered correctly according to what you gave up until then...

[gigiz]

You have reason,
that vg i have PV limit ....
But why i don't mirror a lvol with striping size of 1 Mb ?
Can i modify a PV LIMIT in my vg?

[Sandman!]

The only way you can modify the max PV limit for your current VG is to re-create the volume group with the "-p 255" switch. This will set the limit of PVs to the maximum which is 255.

cheers!