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4.2. Configuration File Blacklist

The blacklist section of the multipath configuration file specifies the devices that will not be used when the system configures multipath devices. Devices that are blacklisted will not be grouped into a multipath device.
In older releases of Red Hat Enterprise Linux, multipath always tried to create a multipath device for every path that was not explicitly blacklisted. In Red Hat Enterprise Linux 6, however, if the find_multipaths configuration parameter is set to yes, then multipath will create a device only if one of three conditions are met:
  • There are at least two non-blacklisted paths with the same WWID.
  • The user manually forces the creation of the device by specifying a device with the multipath command.
  • A path has the same WWID as a multipath device that was previously created (even if that multipath device does not currently exist). Whenever a multipath device is created, multipath remembers the WWID of the device so that it will automatically create the device again as soon as it sees a path with that WWID. This allows you to have multipath automatically choose the correct paths to make into multipath devices, without have to edit the multipath blacklist.
    If you have previously created a multipath device without using the find_multipaths parameter and then you later set the parameter to yes, you may need to remove the WWIDs of any device you do not want created as a multipath device from the /etc/multipath/wwids file. The following shows a sample /etc/multipath/wwids file. The WWIDs are enclosed by slashes (/): 
    # Multipath wwids, Version : 1.0
# NOTE: This file is automatically maintained by multipath and multipathd.
# You should not need to edit this file in normal circumstances.
#
# Valid WWIDs:
/3600d0230000000000e13955cc3757802/
/3600d0230000000000e13955cc3757801/
/3600d0230000000000e13955cc3757800/
/3600d02300069c9ce09d41c31f29d4c00/
/SWINSYS  SF2372         0E13955CC3757802/
/3600d0230000000000e13955cc3757803/
With the find_multipaths parameter set to yes, you need to blacklist only the devices with multiple paths that you do not want to be multipathed. Because of this, it will generally not be necessary to blacklist devices.
If you do need to blacklist devices, you can do so according to the following criteria:
By default, a variety of device types are blacklisted, even after you comment out the initial blacklist section of the configuration file. For information, see Section 4.2.2, “Blacklisting By Device Name”.

4.2.1. Blacklisting by WWID

You can specify individual devices to blacklist by their World-Wide IDentification with a wwid entry in the blacklist section of the configuration file.
The following example shows the lines in the configuration file that would blacklist a device with a WWID of 26353900f02796769. 
blacklist {
       wwid 26353900f02796769
}