scsimgr_esdisk.7 (2010 09)

s
scsimgr_esdisk(7) scsimgr_esdisk(7)
• least_cmd_load
The LUN path with the least number of active I/O requests is selected to execute the next I/O. This
policy is appropriate when the paths to the LUN exhibit asymmetric latency characteristics. The
load is distributed to optimize the bandwidth on each LUN path.
•
cl_round_robin
(cell aware round robin)
This load balancing policy is applicable to HP cell-based platforms. The LUN paths are selected in
a round robin manner within the locality of CPU on which the I/O was initiated, to ensure that
memory access latencies are optimized.
•
preferred_path
The LUN path set in the preferred_path
attribute is preferably used for I/O transfer. If this
LUN path is not available or if the
preferred_path attribute was not set, any other path is
selected for I/O transfer. This policy is useful for certain disk arrays, where some paths may be
optimized for I/O transfer to certain LUNs.
The
preferred_path
attribute can be set with the hardware path, or the combination of the class
and instance number of the preferred LUN path. For example for a LUN path with instance
number 100, the combination of class and instance number is:
lunpath100. In a normal output
display for this attribute, both the hardware path and the combination of class and instance number
of the preferred LUN path are displayed (Example:
0/4/1/0.0x210000203726a3af.0x0(lunpath100)
). In scriptable output for this attribute,
only the hardware path of the preferred LUN path is displayed (Example:
0/4/1/0.0x210000203726a3af.0x0
).
•
closest_path
The LUN path is selected based on its affinity with the CPU issuing the I/O so as to minimize
latency. This policy is more appropriate on cell based platforms.
•
pref_tport
LUN paths to the target port set in the pref_tport attribute are preferably used for I/O transfer
in a round robin manner, when the I/O load balancing policy is set to pref_tport. If no LUN
path to the preferred target port is available, or if the pref_tport attribute is not set, any other
path is selected for I/O transfer. This policy is appropriate for certain disk arrays, where some tar-
get ports are optimized for I/O transfer to certain LUNs.
•
weighted_rr
Weighted Round Robin. I/Os are distributed between the LUN paths in a round robin manner and
according to the weight assigned to each path (via the LUN path attribute wrr_path_weight
). A
number of I/Os corresponding to the weight of the path is transferred on the path before another
path is selected.
EXAMPLES
To display
scsimgr esdisk plug-in general help and supported commands:
scsimgr -h -d esdisk
To get esdisk driver global statistics:
scsimgr get_stat -d esdisk
To clear esdisk driver global statistics:
scsimgr clear_stat -d esdisk
To get esdisk driver global status information:
scsimgr get_info -d esdisk
To display information about esdisk driver global attributes:
scsimgr get_attr -d esdisk
To set the I/O load balancing policy for disk0 to preferred_path and set the I/O path to be used
preferably:
scsimgr set_attr -D /dev/rdisk/disk0 -a load_bal_policy=preferred_path
6 Hewlett-Packard Company − 6 − HP-UX 11i Version 3: September 2010