decrease logical volume

[szhiyong]

Hi,

I try to use sam to decrease the logical volume. I found there is only "increase logical volume" in the sam.

Would someone please to tell me how to decrease the logical volume?

thanks a lot.

zhiyong

[Andreas Voss · Accepted solution]

Hi,

if you don't have Online/JFS you cannot shrink a log. volume / filesystem.
You have to backup the data (filesystem) of the log. volume, umount , remove log. volume, recreate log. volume with new size, make filesystem on log. volume (newfs) , mount again and restore the backuped data.

Regards

[Animesh Chakraborty]

Hi,
#lvreduce -L (size in MB) /dev/vgxx/lvolx

LVM does not store any information about which physical extents within
a logical volume contain useful data; therefore, reducing the space
allocated to a logical volume without doing a prior backup of the data
could lead to the loss of useful data. The lvreduce command on a
logical volume containing a file system of greater length than the
size being reduced to will cause data corruption.

To reduce a logical volume being used for swap, that swap area must
not be currently in use.

See man lvreduce for details.

Cheers
Animesh

[Peter Kloetgen]

Hi,

if you don't have Online JFS, it's not possible to decrease a logical volume. You could do something instead:

make a backup of the logical volume, after that remove the old logical volume, create a new one and restore the backup into the new logical volume.

To find out, if you use Online JFS, simply have a look into your /etc/fstab.

Allways stay on the bright side of life!

Peter

[Jose Juan]

Hi.

# tar -c /myfs
# umount /myfs
#newfs -F vxfs -s xxxxx /dev/vg01/rmyfs
#mount /myfs
#tar -x /myfs
#bdf /myfs

with this you are reducing the file system "myfs" that is JFS (without online JFS)

#lvreduce -L xx /dev/vg01/myfs

with this terminate of reducing the logical volume. Be careful, before make the lvreduce be sure that you were reducing the file system.

Good Luck.
Jota.

[K.Vijayaragavan.]

See the man page of command "lvreduce"

If you are not having Online JFS , reducing a logical volume will wash out the data in it.

However you can take backup and reduce the required voulume and once you have reduced it then restore from backup.

Ex.

Decrease the logical volume size by decreasing the number of logical extents allocated to it.

"lvreduce -l 100 /dev/vg01/lvol3" will reduce the logical extents allocated for /dev/vg01/lvol1 to 100 numbers.

see also the man page of command "lvdisplay" ;
to get the current characteristics of the logical voulme which includes the extent size and the current extent allocated.

-K.Vijay

[K.Vijayaragavan.]

HPUX system administration Tasks manual should help you.
See the link,

http://www.docs.hp.com/cgi-bin/fsearch/framedisplay?top=/hpux/onlinedocs/B2355-90672/B2355-90672_top.html&con=/hpux/onlinedocs/B2355-90672/00/00/1-con.html&toc=/hpux/onlinedocs/B2355-90672/00/00/1-toc.html&searchterms=system%7cadministration%7ctasks&queryid=20020303-234636


-Vijay

[Trond Haugen]

Of course if you have enough diskspace in the VG; create a new lvol, mount it and copy the data over, then remove the "old" lvol. remember to correct fstab.

Regards,
Trond

[szhiyong]

Hi,

Thanks a lot for all your help. I really appreciated it.

Have a good day.

zhiyong