Stripped LV and lvextend

[RAC_1]

I have a lv created with -D y -s g.
lvmpvg has 3 disks now and is full.
If I want to exted it i will have to add a pv and recreate lv with 4 pvs. right? cause strict aloocation will not allow me if I add a pv.

what if I want this lv under SG? does it mean that everytime I want to extend it I will have to recreate the LV? and moreover if there are more pvs it is a pain to do this. not to forget unavailablity of LV.

or Can I do lvchange -s n and add pv enable lvchange -s y?

(I have online JFS)
I think I am right.

Need some info.

[Sridhar Bhaskarla]

Hi Anil,

You said your lvmpvg has 3 disks?. Does this mean your lv is extent striped across 3 disks?.

If so, then you only need to add three more disks. Not 4.

Once you add three more disks, then you can be able to extend your lv.

-s option has nothing to do with serviceguard.

Once you add the PVs and extended the lvol, then export the volume group and import it back on the other system.

Update /etc/lvmpvg on the other system too. You can simply edit and make modifications.

-Sri

[RAC_1]

Shridhar,

Does it mean that if I have 6(for example) pvs in lvmpvg and my lv is full I will have to add 6 more in order to extend? That will be a pain as I have nearly 20 pvs. in lv.

[Sridhar Bhaskarla]

Hi Anil,

Nop. Do an lvdisplay -v on your logical volume and notedown the PVs. You will need to add so many PVs in order to extend the Lvol.

If you used -s g, that indicates that you were doing mirroring also.

Anytime you can turn off Distributed feature and PVGstrict feature. However, you will not get the performance gain for the data that is being accessed to/from the disks that were added after taking those options out.

-Sri

[RAC_1]

pardon my knowledge, but -s g does not do mirroring. it is done with -m right?

even adding a pvs (lvdisplay -v pv's) is a pain.

This is not flexible way.

[Sridhar Bhaskarla]

I said "indicates". -m does. But -s g will make sure that mirrors go into a different PVG. In otherwords it will ensure that the mirrors won't share the same PVG.

-D y -s g is used in conjunction with -m 1 to create extent based mirrors.

I agree it is a pain. But that is what we want right?. Mirroring + Striping? Without VxVM, that's the best you can do with LVM.

-Sri

[RAC_1]

I misread your statement.

I would not go for it. any way this lv is from 0+1 raid.

For better performance from this lv I would rather delete and recreate it than to do -D -s g.

for this lv there are 20 pvs and disk io for some disks is very high and for other it is not. That is why I was thinking of this.

Anyway How VxVM would have helped me in this regard?

[Sridhar Bhaskarla]

Anil,

I can be very easily confused. You said you created them with -D y and -s g options And you want to recreate them?. Am I missing something?

-Sri

[RAC_1]

Sorry I messed up something the one was created with -D -s g.

On this I am observing disk io problems as mentioned.

I am asking what if I create new one with those options and without those options?

(I will copying data from the old lv to this new one and I do not want disk io problem on this.)

How VxVM would have helped me?
and what if

[RAC_1]

Sorry I messed up something the one was created with -D -s g.

On this I am observing disk io problems as mentioned.

I am asking what if I create new one with those options and without those options?

(I will copying data from the old lv to this new one and I do not want disk io problem on this.)

How VxVM would have helped me?
and what if

[Sridhar Bhaskarla · Accepted solution]

Anil,

You really have to understand how the backend is working before you do anything on your side.

Note down the setup on the disk system and do the planning carefully. You can still stripe. But you need to make sure that you don't take LUNs from the same disk group for the stripe set. Else it will counterbalance the striping on the disksystem and that can have adverse affects on the performance.

-Sri

[RAC_1]

Thanks shridhar. I wasted lot of your time it seems.