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can't use LVM2 - "Failed to write physical volume"?

linux-lvm Tomasz Chmielewski 1 participant 2 messages Jan 9, 2008 – Jan 10, 2008

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Tomasz Chmielewski

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It seems to me that for some reason it's not possible to create a physical volume on a DRBD device. Below, we can see that running "pvcreate" succeeds and than fails, then it succeeds again etc.:

# pvcreate -d -v /dev/drbd0
    Set up physical volume for "/dev/drbd0" with 976544952 available 
sectors
    Zeroing start of device /dev/drbd0
  Physical volume "/dev/drbd0" successfully created
# pvcreate -d -v /dev/drbd0
    Wiping cache of LVM-capable devices
    Set up physical volume for "/dev/drbd0" with 976544952 available 
sectors
    Zeroing start of device /dev/drbd0
  Failed to write physical volume "/dev/drbd0"
# pvcreate -d -v /dev/drbd0
    Set up physical volume for "/dev/drbd0" with 976544952 available 
sectors
    Zeroing start of device /dev/drbd0
  Physical volume "/dev/drbd0" successfully created

Running vgcreate fails:

# vgcreate san2_data /dev/drbd0
  No physical volume label read from /dev/drbd0
  /dev/drbd0 not identified as an existing physical volume
  Unable to add physical volume '/dev/drbd0' to volume group 'san2_data'.

This is the setup used:

encrypted /dev/sdb -> unencrypted /dev/mapper/san2_crypt -> partition /dev/mapper/san2_crypt1 -> /dev/drbd0

I can create physical volume on /dev/mapper/san2_crypt2 (no DRBD) just fine.

The machine is running Debian Etch on a 2.6.23.12 kernel.

# lvm version
  LVM version:     2.02.07 (2006-07-17)
  Library version: 1.02.08 (2006-07-17)
  Driver version:  4.11.0

I found a similar post, where DRBD wasn't used:

http://linux.derkeiler.com/Mailing-Lists/Ubuntu/2006-11/msg00414.html

Any clues why this happens?

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Tomasz Chmielewski
http://wpkg.org
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Re: [linux-lvm] can't use LVM2 - "Failed to write physical volume"? [SOLVED]

Quoted 8 lines · Tomasz Chmielewski

It seems to me that for some reason it's not possible to create a physical volume on a DRBD device. Below, we can see that running "pvcreate" succeeds and than fails, then it succeeds again etc.:

# pvcreate -d -v /dev/drbd0
    Set up physical volume for "/dev/drbd0" with 976544952 available 
sectors
    Zeroing start of device /dev/drbd0
  Physical volume "/dev/drbd0" successfully created
Quoted 6 lines
# pvcreate -d -v /dev/drbd0
    Wiping cache of LVM-capable devices
    Set up physical volume for "/dev/drbd0" with 976544952 available 
sectors
    Zeroing start of device /dev/drbd0
  Failed to write physical volume "/dev/drbd0"

Looks like LVM doesn't like some raw devices?

I added a partition to /dev/drbd0 with fdisk.

Then, I added a drive mapping with kpartx.

It works fine now.

# kpartx -a -v /dev/drbd0
add map drbd0p1 : 0 976543092 linear /dev/drbd0 63
# pvcreate -d -v /dev/mapper/drbd0p1
    Set up physical volume for "/dev/mapper/drbd0p1" with 976542708 
available sectors
    Zeroing start of device /dev/mapper/drbd0p1
  Physical volume "/dev/mapper/drbd0p1" successfully created

Anyway, why does it fail if I want to set up LVM on raw DRBD device? A bug or a feature?

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Tomasz Chmielewski
http://wpkg.org