Problem with vgscan and md

Hello,
I found a probable bug in vgscan up to LVM 1.0.5 due to lv device nodes renumbering

i found the problem in a shared storage environment, but it can be reproduced on a single machine

the problem can be reproduced with 2 md devices
create 2 vg each composed of 1 md device
let's say
VG /dev/vg00
Device 109:0
LV /dev/vg00/lvol1
Device 58:0
LV /dev/vg00/lvol2
Device 58:1
LV /dev/vg00/lvol3
Device 58:2
PV /dev/md0

VG /dev/vg01
Device 109:1
LV /dev/vg01/lvol1
Device 58:3
LV /dev/vg01/lvol2
Device 58:4
LV /dev/vg01/lvol3
Device 58:5
PV /dev/md1

now deactivate all VGs
raidstop /dev/md0
run vgscan -v

you have

VG /dev/vg01
Device 109:0
LV /dev/vg01/lvol1
Device 58:0
LV /dev/vg01/lvol2
Device 58:1
LV /dev/vg01/lvol3
Device 58:2
PV /dev/md1

vgchange -a y /dev/vg01

now raidstart /dev/md0

you need to run vgcan again, to see vg00

vgscan renumbers device node for vg00 so you get

VG /dev/vg00
Device 109:0
LV /dev/vg00/lvol1
Device 58:0
LV /dev/vg00/lvol2
Device 58:1
LV /dev/vg00/lvol3
Device 58:2
PV /dev/md0

vgscan cannot renumber device nodes for vg01 (which is active) so you also get

VG /dev/vg01
Device 109:0
LV /dev/vg01/lvol1
Device 58:0
LV /dev/vg01/lvol2
Device 58:1
LV /dev/vg01/lvol3
Device 58:2
PV /dev/md1

so we got two DIFFERENT vgs with the SAME device files

the need to run vgscan is due to having a shared storage so i might want to activate the md devices and vg devices on different nodes

Regards,
Luca

Luca Berra -- [email protected]

Luca,

I tried to reproduce this here with the 1.0.5 and failed.

1.0.5 vgscan only changes minors if there's minor # clashes _and_ if it is run with option "-f" in order to keep minors persistent by default.

So I deativated all VGs and stopped the device for the first one. There was no reason for vgscan to reallocate the device minors because there's no clash. After starting the device again and running vgscan, both VGs were accessable fine.

An automatic reallocation of device numbers took place in vgscan up to version 1.0.
Maybe this is an older tool version?

Regards,
Heinz -- The LVM Guy --

*** Software bugs are stupid.
Nevertheless it needs not so stupid people to solve them ***

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Heinz Mauelshagen Sistina Software Inc.
Senior Consultant/Developer Am Sonnenhang 11
56242 Marienrachdorf Germany
[email protected] +49 2626 141200

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