[linux-lvm] can't use LVM2 - "Failed to write physical volume"?

[linux-lvm] can't use LVM2 - "Failed to write physical volume"?

[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

# 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?


-- 
Tomasz Chmielewski
http://wpkg.org

Re: [linux-lvm] can't use LVM2 - "Failed to write physical volume"? [SOLVED]

[Tomasz Chmielewski]

Tomasz Chmielewski schrieb:
> 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"

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?



-- 
Tomasz Chmielewski
http://wpkg.org