Can I add an alternate disk online ?

[Juan Manuel López]

Hi ALL
I Want to add an alternate link to a vg ussing vgextend, so I do not want to unmount the filesystem or unactivate the vg with vgchange -a n /dev/vgxx
May cause impact to vg running add an alternate disk ?
Thanks in advance.
Juanma.

[Matti_Kurkela · Accepted solution]

Yes, alternate links can be added/removed while filesystem is mounted and vg is active (vgchange -a y) or active/exclusive (vgchange -a e). Last year we did a largish SAN migration where this was essential.

If the vg is activated _for shared access_ (vghange -a s) it seems you cannot use vgextend nor vgreduce. I don't have any clusters with disks in shared access mode so I don't have any experience with this: it's just what the manual says.

[eran maor]

Hi

no problem , you can extend your vg after adding the disk , dont forget to do pvcreate -f to this disk .

remember that if you want to increase your file system you will need onlineJfs or to umount the filesystem , do a lvextend and extendfs after that .

but just to add a disk to your volumegroup , this can be done online .

eran maor

[Juan Manuel López]

Eran, If I make a pvcreate to the new disk, I think this will destroy all lvm information on disk...This is not what I want.
What I want is to add the alternate disk path ( because I can see the same disk by both fiber channel ) to a vg without dismount fs or inactivate vg with vgchange.
Thanks to matti. I think is the rigth answer to my question..Thanks all

Juanma.

[Ameet_HP]

Yes, you can add Alternate Disk Link in VG using vgextend. This never requires to umount the filesystem or deactivate VG. Its always safe to add Alternate link by the time you add that disk in VG. This will help to access the disk with alternate link eventhough primary link is failed while booting the system or any other time.

-Ameet

[SS_6]

Hi Juanma,
Yes, you can do it online, no problem...DO man on vgextend. Command will be like this
#vgextend /dev/vgxx /dev/dsk/cxtxdx
and do
#vgdisplay -v /dev/vgxx
You will see the alternate link with the same physical disk.

[Sanjay_6]

Hi,

If you just addiing alternate pathing to the same disk through a differnet fiber card, you can do so online without worrying about performance and any such issue.

And you don't have to do pvcreate. You do a pvcreate when you want to add another disk which would be a mirror copy of the first disk and that is not the case over here.

Hope this helps.

Regds