Configure lvm2 with drbd

Hi,

I'm trying to configure lvm2 on top of drbd. I've configured drbd
(/dev/drbd0 and /dev/drbd1) and put them as primary node, but when I try to create a physical volume this is what it does happens

pvcreate /dev/drbd0
Physical volume "/dev/drbd0" successfully created
pvdisplay
--- NEW Physical volume ---
PV Name /dev/md4
VG Name
PV Size 129,45 GB
Allocatable NO
PE Size (KByte) 0
Total PE 0
Free PE 0
Allocated PE 0
PV UUID MtxjHy-8zfW-i9nq-TJA4-b6F9-jtcW-FkanLB

/dev/md4 is the raid device over was configured drbd0.

Why /dev/md4 it's taken as PV Name?

Thanks in advance

Best regards

Mariano

It's trying to be helpful! Normally people build MD devices out of other devices and so LVM uses the MD in preference to other devices it finds with the same UUID.

You'll need to exclude the MD device in the /etc/lvm/lvm.conf filters entry. something like:

filter =[ "r/md4/" ]

Patrick

Registered Address: Red Hat UK Ltd, Amberley Place, 107-111 Peascod Street,
Windsor, Berkshire, SL4 ITE, UK.
Registered in England and Wales under Company Registration No. 3798903

Thanks so much! now it does work ok.

Best regards

Mariano

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Hi Mariano,

LVM2 identifies devices using labels written on the disks. So, if md4 is the underlying device for your drbd devices, when lvm2 scans /dev looking for labels it finds the label on md4 first and uses that.

You can control this using lvm2's filtering options.

See the man page for lvm.conf for the full details, but editing /etc/lvm/lvm.conf and changing the filter line from:

        filter = [ "a/.*/" ]

to:

        filter = [ "a|/dev/drdb|", "r|/dev/md|", "a|.*|" ]

Should accept all drdb devices as physical volumes, reject any software raid (md) devices, and accept everything else.

This should work if you only have PVs on drdb or other device types and not on any plain md devices. If you have a mix of the types you will need to create a more specific filter line for your system.

Regards,
Bryn.
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