/ 10.2. Configuring Eligible LVM2 Devices Explicitly
	Chapter 10. Cluster LVM		10.3. For More Information

Configuring Eligible LVM2 Devices Explicitly

When several devices seemingly share the same physical volume signature (as can be the case for multipath devices or drbd), it is recommended to explicitly configure the devices which LVM2 scans for PVs.

For example, if the command vgcreate uses the physical device instead of using the mirrored block device, DRBD will be confused which may result in a split brain condition for DRBD.

To deactivate a single device for LVM2, do the following:

Edit the file /etc/lvm/lvm.conf and search for the line starting with filter.
The patterns there are handled as regular expressions. A leading “a” means to accept a device pattern to the scan, a leading “r” rejects the devices that follow the device pattern.
To remove a device named /dev/sdb1, add the following expression to the filter rule:
```
"r|^/dev/sdb1$|"
    
```
The complete filter line will look like the following:
```
filter = [ "r|^/dev/sdb1$|", "r|/dev/.*/by-path/.*|", "r|/dev/.*/by-id/.*|", "a/.*/" ]
    
```
A filter line, that accepts DRBD and MPIO devices but rejects all other devices would look like this:
```
filter = [ "a|/dev/drbd.*|", "a|/dev/.*/by-id/dm-uuid-mpath-.*|",
"r/.*/" ]
```
Write the configuration file and copy it to all cluster nodes.