HP-UX Reference (11i v3 07/02) - 7 Device (Special) Files, 9 General Information, Index (vol 10)

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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 I/O path set in the preferred_path attribute is preferrably used for I/O transfer. If this I/O 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, which may exhibit some performance degrada-

tion if I/Os are transferred via several I/O paths to a LUN simultaneously.

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 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

-a preferred_path=0/3/1/0.0x21000020371972eb.0x0

To add a settable attribute scope corresponding to all disk devices from HP with product identiﬁer "MSA

VOLUME", for allowing modiﬁcation of some settable attribute at this scope

scsimgr ddr_add -N "/escsi/esdisk/0x0/HP /MSA VOLUME "

To persistently change the default I/O load balancing policy, I/O timeout, and maximum concurrent I/O for

all disk devices from HP with product identiﬁer "MSA VOLUME"

scsimgr save_attr -N "/escsi/esdisk/0x0/HP /MSA VOLUME "

-a load_bal_policy=least_cmd_load -a esd_secs=60

-a path_fail_secs=60

To disable write cache, Persistent Reservation and 16 bytes read/write CDB for all disk devices bound to the

esdisk driver

scsimgr set_attr -N /escsi/esdisk -a disable_flags=’WCE PR RW16’

AUTHOR

SCSI class driver esdisk plug-in for scsimgr was developed by Hewlett Packard Company.