multipath device. This should not cause any difficulties if you use LVM to create logical devices
from the multipath device, but if you require that your multipath device names be consistent in
every node in the cluster you perform one of the following procedures:
• Use the
alias
option in the
multipaths
section of the multipath configuration file to set the
name of the multipath device. The
alias
for the multipath device is consistent across all the
nodes in a cluster. For information on the
multipaths
section of the multipath configuration
file, see see
Section 4, “Multipaths Device Configuration Attributes”
.
• If you want the system-defined user-friendly names to be consistent across all nodes in the
cluster, set up all of the multipath devices on one machine. Then copy the
/var/lib/multipath/bindings
file from that machine to all the other machines in the
cluster.
3. Multipath Device Attributes
In addition to the
user_friendly_names
and
alias
options, a multipath device has numerous
attributes. You can modify these attributes for a specific multipath device by creating an entry
for that device in the
multipaths
section of the multipath configuration file. For information on
the
multipaths
section of the multipath configuration file, see see
Section 4, “Multipaths Device
Configuration Attributes”
.
4. Multipath Devices in Logical Volumes
After creating multipath devices, you can use the multipath device names just as you would use
a physical device name when creating an LVM physical volume. For example, if
/dev/mapper/mpath0
is the name of a multipath device, the following command will mark
/dev/mapper/mpath0
as a physical volume.
pvcreate /dev/mapper/mpath0
You can use the resulting LVM physical device when you create an LVM volume group just as
you would use any other LVM physical device.
When you create an LVM logical volume that uses active/passive multipath arrays as the
underlying physical devices, you should include filters in the
lvm.conf
to exclude the disks that
underlie the multipath devices. This is because if the array automatically changes the active
path to the passive path when it receives I/O, multipath will failover and failback whenever LVM
scans the passive path if these devices are not filtered. For active/passive arrays that require a
command to make the passive path active, LVM prints a warning message when this occurs.
To filter all SCSI devices in the multipath configuration file (
lvm.conf
), include the following filter
in the
devices
section of the file.
filter = [ "r/disk/", "r/sd.*/", "a/.*/" ]
Chapter 2. Multipath Devices
8
Summary of Contents for DEVICE-MAPPER MULTIPATH 5.2
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