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78 Chapter 4
Configuring and Using the 9900 Subsystem
4.5 Open Systems Operations
4.5.1 Command Tag Queuing
The 9900 supports command tag queuing for open-system devices. Command tag queuing
enables hosts to issue multiple disk commands to the fibre-channel adapter without having
to serialize the operations. Instead of processing and acknowledging each disk I/O
sequentially as presented by the applications, the 9900 subsystem processes requests in the
most efficient order to minimize head seek operations and disk rotational delay.
Note: The queue depth parameter may need to be adjusted for the 9900 devices. Please
refer to the appropriate 9900 configuration guide for queue depth requirements and
instructions on changing queue depth and other related system and device parameters (refer
to Table 4.7 for a list of the 9900 open-system configuration guides).
4.5.2 Host/Application Failover Support
The 9900 supports many industry-standard products which provide host and/or application
failover capabilities (e.g., HP
®
MC/ServiceGuard, VERITAS
®
First Watch
®
, HACMP, Microsoft
®
Cluster Server, Novell
®
Cluster Server, Sun Cluster, TruCluster, VMSCluster). For the latest
information on failover and LVM product releases, availability, and compatibility, please
contact your Hitachi Data Systems account team.