LVM mirror configuration

[johnsonpk]

Hi Senthil/Suraj :



Reg:>># lvcreate -L 1000 /dev/dsk/c3t2d0



>># lvextend -m 1 /dev/vg01/lvol3 /dev/dsk/c5t1d2



There is no way to specify the PV during lvcreation as far as I know..so you may need to follow the below steps to control the LE on the disks as per your wish..



1)Create a logical volume with size 0

#lvcreate -n lvol3 /dev/vg01

2)extend the lv to the disk you desired with correct size

#lvextend -L 1000 /dev/vg01/lvol3 /dev/dsk/c3t2d0

3)create a mirror copy in the scond disk

# lvextend -m 1 /dev/vg01/lvol3 /dev/dsk/c5t1d2



There is many ways to archive this ..one way is to use the lvmpvg and create lv with pvg strict policy





Thanks!!

Johnson

[senthil_kumar_1]

Hi Johnson Punniyalingam ,

A)so you are telling that we should not follow below steps to add new mirror disks?

3) Adding new disk as physical disk

#pvcreate -f /dev/rdsk/c3t6d0

4) Including new disk into vg01

#vgextend /dev/vg01 /dev/dsk/c3t6d0

5) To create new mirror:

# lvextend -m 1 /dev/vg01/lvol3 /dev/dsk/c3t6d0




B)what is the purpose of these commands?

# vgchange -a y vgXX (by default VGs are backuped then why we are using this command.)

# vgsync vgxx


Hi johnsonpk,

C)we should not use like below?

# lvcreate -L 1000 /dev/vg01/lvol3 /dev/dsk/c3t2d0

D)Instead we have to use below method if we want to create the logical volume in spcified disk?

1)Create a logical volume with size 0
#lvcreate -n lvol3 /dev/vg01
2)extend the lv to the disk you desired with correct size
#lvextend -L 1000 /dev/vg01/lvol3 /dev/dsk/c3t2d0

Guys pls clarify myself.

[R.K. #]

Hello Senthil,

See what happens when I tried below command:

root> lvcreate -L 1000 /dev/vg01/lvol31 /dev/dsk/c2t1d0
Volume group "/dev/vg01/lvol31" does not exist in the "/etc/lvmtab" file.
Volume group "/dev/vg01/lvol31" does not exist in the "/etc/lvmtab_p" file.

So that clearly shows we need to create the LV first & then extend it by lvextend command.


You are correct, first create Lvol of size 0 and then extend it.
#lvcreate -n lvol3 /dev/vg01
#lvextend -L 1000 /dev/vg01/lvol3 /dev/dsk/c3t2d0

Man lvcreate also do not have any entry for lvcreate with disk name.


And for vgchange -a y vgXX, it reactivates the VG and activate each specified volume group and all associated physical and logical volumes for read-write access. So in turns it syncronizes the VG. So somtime we would not require "vgsync" command after "vgchange -a y vgXX".

Hope this helps.
R.K.

[avizen9]

Hello Senthil,
you dont need to confuse here, just follow basic steps for mirroring as mentioned. if you face any difficulty let us know, thanks,

[johnsonpk]

>>>Hi Johnson Punniyalingam ,

>>>A)so you are telling that we should not follow below steps to add new mirror disks? ..

no ..The below steps are ok

3) Adding new disk as physical disk

#pvcreate -f /dev/rdsk/c3t6d0

4) Including new disk into vg01

#vgextend /dev/vg01 /dev/dsk/c3t6d0

Then...

5)Create a logical volume with size 0
#lvcreate -n lvol3 /dev/vg01
6)extend the lv to the disk you desired with correct size
#lvextend -L 1000 /dev/vg01/lvol3
7)create a mirror copy in the scond disk
# lvextend -m 1 /dev/vg01/lvol3


Hope you are clear now..


Thanks
Johnson

[Ganesan R]

Hi Senthil,

I reiterate you to read this document instead making yourself confused.

http://docs.hp.com/en/5992-4589/5992-4589.pdf

It's a good document on LVM.

[senthil_kumar_1]

Hi All,

I have following doubts, please clarify me.

1)Can i use bleow command to add 2 mirrors:

# lvextend â m 2 /dev/vg01/lvhome


2)From that, how to remove only one mirror (for example mirror - 1)?

[Pete Randall]

1) yes.

2) lvreduce -m 1 blah...blah...blah


Pete