[linux-lvm] Cannot create PV on /dev/dm-NN (/dev/dm-N works)

[Michael Fladischer]

Hi,

I'm unable to create PVs on Multipath-Volumes that are available at
/dev/dm-NN where N~[0-9] but I can create them on single digit devices
like /dev/dm-9:

# pvcreate /dev/dm-6
Physical volume "/dev/dm-6" successfully created.

# pvcreate /dev/dm-16
Device /dev/dm-16 not found (or ignored by filtering).

My Version of LVM is 2.02.168 from Debian 9.
The filter ist set to a permissive value:
filter = [ "a|.*|" ]
global_filter = [ "a|.*|" ]

Any ideas why two or more digits in the device path can cause it to be
filtered by pvcreate?

Cheers,

[Zdenek Kabelac]

Post by Michael Fladischer
Hi,
I'm unable to create PVs on Multipath-Volumes that are available at
/dev/dm-NN where N~[0-9] but I can create them on single digit devices
# pvcreate /dev/dm-6
Physical volume "/dev/dm-6" successfully created.
# pvcreate /dev/dm-16
Device /dev/dm-16 not found (or ignored by filtering).
My Version of LVM is 2.02.168 from Debian 9.
filter = [ "a|.*|" ]
global_filter = [ "a|.*|" ]
Any ideas why two or more digits in the device path can cause it to be
filtered by pvcreate?

Hi


lvm2 is detecting multipath 'component' devices - those are not allowed to be
used for pvcreate.

You can use 'pvcreate -vvv' to get more information - there will be printed
the reason why devices are rejected....

Eventually if you can't figure this out yourself - provide this trace in
attachment.


Regards

Zdenek

[Roger Heflin]

I suggest you should never directly be touching the /dev/dm* devices
via that name.

Always touch the actual named device (/dev/mpath, /dev/vgname/lv A
given dm device can be a number of other devices (lv,s, mpath, mpath
components, encrypted device, md raid, and probably some others).

From just the dm* name you really don't know which kind of device it

is, and there is a lot of risk of confusion and/or data loss.

I have debugged situations were someone went in and partitioned all of
their /dev/dm* devices and some of those devices were actually the
LV's and others were they created PV's on other LV's. Without a few
commands you cannot easily know what the dm* device is, so access it
via the more sensibly named device.

Post by Michael Fladischer
Hi,
I'm unable to create PVs on Multipath-Volumes that are available at
/dev/dm-NN where N~[0-9] but I can create them on single digit devices
# pvcreate /dev/dm-6
Physical volume "/dev/dm-6" successfully created.
# pvcreate /dev/dm-16
Device /dev/dm-16 not found (or ignored by filtering).
My Version of LVM is 2.02.168 from Debian 9.
filter = [ "a|.*|" ]
global_filter = [ "a|.*|" ]
Any ideas why two or more digits in the device path can cause it to be
filtered by pvcreate?

Hi
lvm2 is detecting multipath 'component' devices - those are not allowed to
be used for pvcreate.
You can use 'pvcreate -vvv' to get more information - there will be printed
the reason why devices are rejected....
Eventually if you can't figure this out yourself - provide this trace in
attachment.
Regards
Zdenek
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[Michael Fladischer]

Post by Zdenek Kabelac
lvm2 is detecting multipath 'component' devices - those are not allowed to be
used for pvcreate.
You can use 'pvcreate -vvv' to get more information - there will be printed
the reason why devices are rejected....

Thanks, I figured it out. As it happens those devices with two digits
had a GPT on them. Once I erased the primary copy at the beginning of
the devices, I was able to use pvcreate on them.

Cheers,