HP XP20000/XP24000 Посібник з конфігурації - Сторінка 35

B Using Veritas Cluster Server to prevent

data corruption

By issuing a Persistent Reserve SCSI-3 command, VCS employs an I/O fencing feature that prevents

data corruption from occurring if cluster communication stops. To accomplish I/O fencing, each node

of VCS registers reserve keys for each disk in a disk group that is imported. The reserve key consists

of a unique value for each disk group and a value to distinguish nodes. When importing a disk group,

each node in a VCS cluster registers the reserve key for all paths of all disks (LUs) in the disk group,

but only 1 node will succeed in reserving the disk group. Example reserve keys for Port 1A are shown

Table 7

on page 37 and example reserve keys for Port 2A are shown in

format of the reserve key is:

node number + disk group-unique information

When the Persistent Reserve command is received by the disk array, the reserve key and Port WWN

of node are registered in the key registration table for each port of the disk array. To avoid duplicate

registrations, the disk array checks the node Port WWN and reserve key and only adds an entry in

its table if the WWN/reserve key combination do not already exist in the table for the port which

received the registration request. Duplicate entries can exist across different ports.

The maximum number of reserve keys that can be registered per port for each disk array is 128.

Attempts to add additional registration keys will fail if the number exceeds this limit. Because of this,

try to limit the number of:

Nodes

Paths to each array port

Disk groups

For example, when adding an LU to increase disk capacity, do not create a new disk group. Instead,

add the LU to one of the existing disk groups (see

For each array port, calculate the number of VCS registration keys needed as follows:

number of WWNs visible to an XP port x number of disk groups = number of registration keys

Where the number of WWNs visible to an XP port = number of hosts x number of WWNs

per XP port.

Figure 4

on page 36, the number of WWNs visible to either port (1A or 2A) is four (WWNa0

and WWNb0 for port 1A and WWNa1 and WWNb1 for port 2A). Therefore, the number of

registration keys will be equal to 4.

Figure 4

on page 36).

XP Disk Array Configuration Guide: Solaris

Table 8

on page 37. The