Dne 26.3.2018 v 08:04 Gang He napsal(a):
Hi Xen,
Gang He schreef op 23-03-2018 9:30:
6) attach disk2 to VM2(tb0307-nd2), the vg on VM2 looks abnormal.
tb0307-nd2:~ # pvs
WARNING: Device for PV JJOL4H-kc0j-jyTD-LDwl-71FZ-dHKM-YoFtNV not
found or rejected by a filter.
PV VG Fmt Attr PSize PFree
/dev/vdc vg2 lvm2 a-- 20.00g 20.00g
/dev/vdd vg1 lvm2 a-- 20.00g 20.00g
[unknown] vg1 lvm2 a-m 20.00g 20.00g
This is normal because /dev/vdd contains metadata for vg1 which includes
now missing disk /dev/vdc .... as the PV is no longer the same.
tb0307-nd2:~ # vgs
WARNING: Device for PV JJOL4H-kc0j-jyTD-LDwl-71FZ-dHKM-YoFtNV not
found or rejected by a filter.
VG #PV #LV #SN Attr VSize VFree
vg1 2 0 0 wz-pn- 39.99g 39.99g
vg2 1 0 0 wz--n- 20.00g 20.00g
This is normal because you haven't removed /dev/vdc from vg1 on
/dev/vdd, since it was detached while you operated on its vg.
7) reboot VM2, the result looks worse (vdc disk belongs to two vg).
tb0307-nd2:/mnt/shared # pvs
PV VG Fmt Attr PSize PFree
/dev/vdc vg1 lvm2 a-- 20.00g 0
/dev/vdc vg2 lvm2 a-- 20.00g 10.00g
/dev/vdd vg1 lvm2 a-- 20.00g 9.99g
When you removed vdd when it was not attached, the VG1 metadata on vdd
was not altered. The metadata resides on both disks, so you had
inconsistent metadata between both disks because you operated on the
shared volume group while one device was missing.
You also did not recreate PV on /dev/vdc so it has the same UUID as when
it was part of VG1, this is why VG1 when VDD is booted will still try to
include /dev/vdc because it was never removed from the volume group on
VDD.
So the state of affairs is:
/dev/vdc contains volume group info for VG2 and includes only /dev/vdc
/dev/vdd contains volume group info for VG1, and includes both /dev/vdc
and /dev/vdd by UUID for its PV, however, it is a bug that it should
include /dev/vdc even though the VG UUID is now different (and the name
as well).
It looks like each PV includes a copy meta data for VG, but if some PV has changed (e.g. removed, or moved to another VG),
the remained PV should have a method to check the integrity when each startup (activated?), to avoid such inconsistent problem automatically.
Hi
I'm not really sure what are you trying to achieve - are you 'validating' that
you cannot foolish lvm2 too easily or something else ?
Simple case is when you have a VG on 2 PV disks. Both PV hold full metadata
for a VG. There are numerous other case - i.e. you can have 1000PVs in single
VG then any update of metadata would require to update 1000 disks - for this
case you can select lower number metadata copies - i.e. randomly or
user-selected PVs only hold VG metadata and rest of PV are without metadata.
The less metadata copies - the less secure it is, but update is faster...
There are no metadata for use stored in your filesystem - VG metadata are
always recorded in PV metadata area.
1.) So when you 1st. remove device and then you run 'pvremove' on this missing
disk, it's kind of pointless operation.
2.) lvm2 command will not let you 'easily' remove PV which is in use by some
LV in your VG
3.) lvm2 supports 2 commands:
'vgreduce --removemissing' (try to make consistent VG when PV is lost)
'vgextend --restoeremissing' (restore missing PV back into VG)
Regards
Zdenek
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