topic Re: lvreduce with many disks in Operating System - HP-UX

lvreduce with many disks

achduliebe — Thu, 29 Sep 2016 14:38:32 GMT

Need some help, for some reason I have encountered this issue and I can not wrap my head around a solution.

The issue I'm having involves a storage migration. I have a volume group with quite a few 100GB LUNs. All of these luns make up one logical volume. I need to mirror that logical volume to new 3Par disks. No issues there, my issue comes in the splitting off of the old LUNs (original luns).

The problem is that when I do the lvreduce to break off the original disks, I don't have enough characters on the command line to accomodate all of the disks I need to split off.

How do I split off (lvreduce) a large number of disks?

Hopefully that makes some sense.

Thanks,

Bryan

Re: lvreduce with many disks

achduliebe — Thu, 29 Sep 2016 15:27:26 GMT

Ok, well I did a bit more digging and found this post:

/t5/LVM-and-VxVM/lvreduce-m-0-multiple-PV-s/td-p/5083917

So basically what I was missing was adding "\" to continue the input line. I don't know why I could not pull that out of my head, as many times as I have used that...

As an FYI, here is what the command would look like:

lvreduce -m 0 /dev/vgXX/lvolYY /dev/disk/disk## /dev/disk/disk## \

/dev/disk/disk## /dev/disk/disk## \

/dev/disk/disk##

Re: lvreduce with many disks

Steven Schweda — Thu, 29 Sep 2016 15:49:46 GMT

> [...] I don't have enough characters on the command line [...]

For some shell or other (which?)? Using some terminal/emulator?
What, exactly, do you think limits what, exactly?

> [...] adding "\" to continue the input line. [...]

Or just keep typing past (whatever you think is) the end of the line?

> [...] can not wrap my head around [...]

It's a line-wrap question, not a head-wrap question.

Re: lvreduce with many disks

Bill Hassell — Thu, 29 Sep 2016 17:02:48 GMT

This is a common misunderstanding about line lengths. Your terminal emulator (SecureCRT, Reflection, PuTTY, xterm...) provides an artificial line length that may be 80 or 100 or more characters. But the right end of the screen is meaningless to the shell which is limited to about 250 characters for an input line. And vi is limited to about 4000 characters on a single line.

Or for lvreduce, you can issue the command several times to remove a few LUNs at a time.

Re: lvreduce with many disks

Steven Schweda — Thu, 29 Sep 2016 18:29:11 GMT

> [...] the shell which is limited to about 250 characters for an input
> line. [...]

This depends on which "the shell" you use. Around here, for example:

rux# uname -a
HP-UX rux B.11.31 U ia64 1678555272 unlimited-user license

And "/bin/sh" stops accepting input at 250 characters, so a command like
"echo <blah, blah, ...> is stopped at a point like this (as seen on an
80-character-wide terminal):

("echo " + 245 characters = 250 characters.)

But GNU bash has no such (low) limit:

1 123456789 123456789 123456789 123456789 123456789 2 123456789 123456789 123456
789 123456789 123456789 3 123456789 123456789 123456789 123456789 123456789 4 12
3456789 123456789 123456789 123456789 123456789 5 123456789 123456789 123456789
123456789 123456789 6 123456789 123456789 123456789 123456789 123456789 7 123456
789 123456789 123456789 123456789 123456789 8 123456789 123456789 123456789 1234
56789 123456789 9 123456789 123456789 123456789 123456789 123456789 A 123456789
123456789 123456789 123456789 123456789 B 123456789 123456789 123456789 12345678
9 123456789 C 123456789 123456789 123456789 123456789 123456789 D 123456789 1234
56789 123456789 123456789 123456789 E 123456789 123456789 123456789 123456789 12
3456789 F 123456789 123456789 123456789 123456789 123456789

("echo " + 779 characters = 784 characters, with no end in sight.)

rux# $0 --version
$0 --version
GNU bash, version 3.2.0(1)-release (ia64-hp-hpux11.31)
Copyright (C) 2005 Free Software Foundation, Inc.

But certainly, using backslash-escaped line breaks, and writing a
script instead of trying to enter such a long line manually (even
employing the new copy+paste technology which I used) makes more sense.

Re: lvreduce with many disks

Torsten. — Thu, 29 Sep 2016 20:33:30 GMT

do a

man lvmpvg

this will help you.