NEC PathManager

Chapter 4 Operating NEC Storage PathManager

[For Windows 2000]

C:\>spscmd -getwatcher

Health check : Enable

Recovery check : Enable

Request interval : 60 sec

Threshold : 60 sec

Timeout duration : 120 sec

C:\>

[For Windows Server 2003]

C:\>spscmd -getwatcher

Health check : Enable

Request interval : 60 sec

C:\>

.1.4 R

Recommended settings for priority

4.1

In a system having a configuration with two paths, there will be only one available path when failures occur

in the path in use. Therefore, setting priority does not have any significant meaning except for when

executing load balancing. However, in a system having a larger number o f paths, attention must be paid to

settings for priority in order to secure smooth switching of paths in case of failures and to secure dynamic load

balancing performance.

When failures occur in a path in use, NEC Storage PathManager attempts to use a path having the second

highest priority. If this path is also experiencing failures, then a path having the third highest priority will

become the next candidate. It may seem rare that more than two paths experience failures at the same time;

however, this can happen depending on system configuration.

In the figure below, the system has a configuration with four paths and two FC switches, and path priorities

are set to 4, 3, 2, and 1 to respective paths from left to right. Therefore, the path having priority 4 is currently

in use. When the left FC switch fails in this system, the path having priority 4 will fail. Therefore, failover

is executed so that the path with priority 3 is be used. However, since the left FC switch has failed, the path

having priority 3 has also failed. As a result, failover is executed again so that the path with priority 2 will be

used. As described above, there will be unnecessary failover processing from the path having priority 4 to

the path having priority 2 since it must be conducted via the path having priority 3. NEC Storage

PathManager takes the longest to recognize path failures when I/O timeout occurs. In such cases, it will take

up to a minute for NEC Storage PathManager to be aware of the failures. So in the above example it may

IV-6