Re: Device Mapper Blacklist

In Linux, Device Mapper is a generic subsystem that provides many kinds of storage management functionality, including:

• multipathing
• software RAID
• disk and partition encryption
• LVM

With "dmsetup ls --tree", you can see all the things Device Mapper is currently doing on your system.

I guess that you're thinking about device-mapper-multipath (dm-multipath for short). In that case, the blacklisting functionality exists in /etc/multipath.conf. You could specify something like this in the blacklist section:

blacklist {
        device {
                vendor "EMC"
                product "SYMMETRIX"
        }
        # put here any other blacklist entries you may want to have
}

You can even put in vendor "EMC" and product ".*" (the regular expression for "any string at all") if you want to exclude all EMC disks.

To whitelist something, either remove the existing blacklist entry for it, or add a "blacklist_exceptions" section with appropriate entries.

Since dm-multipath has quite a lot of compiled-in defaults, you may need this command to review the currently running configuration in complete form:

echo "show config" | multipathd -k | less

If you really need to blacklist some devices from LVM, then the "filter" keyword in /etc/lvm/lvm.conf can do that.

I have no experience in mixing PowerPath with dm-multipath, but I think the dm-multipath configuration syntax can easily handle your requirements.