User guide

© DataDirect Networks 2011. Multipath (V1.8) User Guide | 15
# multipath -ll
mpath19 (360001ff0721160000000002688e10002) dm-2 DDN,S2A 6620
[size=21T][features=1 queue_if_no_path][hwhandler=0][rw]
\_ round-robin 0 [prio=50][active]
\_ 1:0:0:2 sdg 8:96 [active][ready]
\_ round-robin 0 [prio=10][enabled]
\_ 2:0:0:2 sdf 8:80 [active][ready]
[size=21T][features=1 queue_if_no_path][hwhandler=0][rw]
^ ^ ^ ^
| | | |___ Device Permissions
| | |___________ Hardware Handler
| |_________________________ Supported Features
|________________________________________________ Size of the DM Device
The features value determines what to do if the path has failed. It is recommended to have
no_path_retry defined in multipath.conf
# multipath -ll
mpath19 (360001ff0721160000000002688e10002) dm-2 DDN,S2A 6620
[size=21T][features=1 queue_if_no_path][hwhandler=0][rw]
\_ round-robin 0 [prio=50][active]
\_ 1:0:0:2 sdg 8:96 [active][ready]
\_ round-robin 0 [prio=10][enabled]
\_ 2:0:0:2 sdf 8:80 [active][ready]
Path Group 1
\_ round-robin 0 [prio=50][active]
^ ^ ^ ^
| | | |_________________ Path Group State
| | |_________________________ Path Group Priority
| |____________________________________ Path Selector and Repeat Count
|___________________________________________ Path Group Level
A Path is the connection from the server (initiator – HBA/HCA) to a specific LUN (target device).
The server will create a device path for each available path to the target device if the device
(LUN) is mapped/masked in such a way that it is available across multiple server initiator ports
(for redundancy, HA, and performance reasons). Thus the server will have multiple paths to the
same target device in this situation.