extend a stripe

[Mark Mitchell]

Here is one that I haven't tested before. If you have say 10 disks in a VG. And you have created a LV that is striped across all 10 disks. Then the day comes where you have used all the space. Can you add 5 disks and extend the LV or does the LV have to be extended onto 10 devices.

[Pete Randall · Accepted solution]

Hi Mark,

If I may quote from the lvextend man page:

"LVM striped logical volumes are always allocated using a strict
allocation policy. Consequently, striped logical volumes may only be
extended by a number extents that is a multiple of disks the logical
volume is striped across. For example, for a logical volume striped
across 3 disks, the logical volume will be extended in increments of 3
extents, with each of the 3 extents allocated on a different disk in
the volume group."


The answer to your question, then, is 10.


Pete

[S.K. Chan]

I haven't either but I think if you stripe it across 10 disks and given the fact that this has to be in strict allocation, the only way it would work is to add another 10 disks (no more no less).

[Mark Mitchell]

I am going to try something, and will then assign points later this afternoon

[Michael Steele_2]

To the best of my unhappy knowledge and unhappy experience, NO.

Ran across this with ASU. This application had a file system with 24 disks within a logical volume stipped at 64 kb and no one would ever clean this file system out. It grew and grew and grew. It grew to 96% and still no one would clean it out.

Then the user found out that they needed to buy another 24 disks to make the file system grow, or, clean it out.

Which do you think they performed?

They bought a whole new disk array rather than clean up this file system and added 24 disks.

And obstinite users that they were, they wouldn't allow for 4 disk pvg's, which is what a lot of people recommended.

So, if you have a physical volume group with 4 disks you can label them and add them in as needed.

1) vgcreate -g pvg0 /dev/vg01 /dev/dsk/c2t9d0 (* First disk into pvg0 *)

2a) vgextend -g pvg0 /dev/vg01 /dev/dsk/c4t8d0 (* additional disk into pvg0 *)

-or-

2b) vi /etc/lvmpvg
(* manually add disks *)

vg01
pvg1
c2t9d0
c4t8d0
c1t9d0 (* add in *)
c3t8d0 (* add in *)

lvcreate -D y -s g -r n /dev/vg01

(* lvcreate determines pvgs w/out specifiying them *)

http://docs.hp.com/cgi-bin/fsearch/framedisplay?top=/hpux/onlinedocs/B9106-90008/B9106-90008_top.html&con=/hpux/onlinedocs/B9106-90008/00/02/208-con.html&toc=/hpux/onlinedocs/B9106-90008/00/02/208-toc.html&searchterms=stripe%7cpvg%7clvcreate&queryid=20030429-185924

[Mark Mitchell]

Thanks all