IBM System Storage DS3500 Introduction And Implementation Manual page 675

Draft Document for Review March 28, 2011 12:24 pm
adapter driver waits a short period of time, approximately 15 seconds, so that the fabric
can stabilize, this occurs when the default setting of "delayed_fail" is set. At that point, if
the FC adapter driver detects that the device is not on the fabric, it begins failing all I/Os
at the adapter driver. Any new I/O or future retries of the failed I/Os are failed
immediately by the adapter until the adapter driver detects that the device has rejoined
the fabric. In single-path configurations, especially configurations with a single path to
a paging device, the delayed_fail default setting is preferred, one such scenario is AIX
server direct attachment to the DS3500 controller host port.
To enable load balancing across multiple Fibre Channel adapters within the Virtual I/O
Servers when using the base AIX MPIO support, set the algorithm to round_robin for each
physical disk as shown in Example 21-8 and Example 21-9.
Note: It is necessary to set the reserve_policy to "no_reserve" (as shown in Example 21-4
and Example 21-5) before setting the algorithm to round_robin.
Example 21-8 Setting the round_robin parameter on VIOS
$ chdev -dev hdisk2 -attr algorithm=round_robin -perm
hdisk2 changed
Example 21-9 Setting the round_robin parameter on AIX
# chdev -l hdisk2 -a algorithm=round_robin -P
hdisk2 changed
Note: MPIO for virtual SCSI devices currently only support failover mode in AIX.
Enable the health check mode for the disk so that the status of the disks is automatically
updated. Health check mode is disabled by default (hckeck_interval=0). As long as it is
disabled the client partition does not update the path status in case of a failure of the
active path. To activate the health check function, use the chdev command, as shown in
Example 21-10 and Example 21-11. In this example, we use a health check interval of 60
seconds. To check for the attribute setting, use the lsattr command.
Note: The path switching also works if the hcheck_interval attribute is disabled, but it is
recommended to have the status updated automatically.
Example 21-10 Changing the health interval parameter on VIOS
$ chdev -dev hdisk2 -attr hcheck_interval=60 -perm
hdisk2 changed
Example 21-11 Changing the health interval parameter on AIX
# chdev -l hdisk2 -a hcheck_interval=60 -P
hdisk2 changed
All this parameters can also be changed from Smitty mpio  MPIO Device
Management  Change/Show MPIO Devices Characteristics.
Chapter 21. AIX 6.1 configuration guide
AIX.fm
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