HP AD510A - StorageWorks Modular Smart Array 1500 cs 2U Fibre Channel SAN Attach Controller Shelf Hard Drive Installation Manual page 23

• Customize the RAID level and striping method to the type of data that will be stored on the
LUN. For example, depending on the number of drives included in an array, the ACU may
suggest RAID 6 (ADG) as the default RAID level, which offers a high level of fault tolerance
and usable disk capacity, but at a significant cost to I/O performance. For comparable fault
tolerance but higher performance, consider using RAID 1+0 when fault tolerance is desired
and performance is more important than usable capacity. Reserve RAID 6 for situations when
fault tolerance is desired, but usable capacity is more important than performance.
• Set the ratio of read cache to write cache to prioritize writing in RAID 1, RAID 1+0, RAID 5,
and RAID 6 (ADG) configurations to improve non-random write performance.
• Set the controller rebuild priority to medium or high to minimize exposure during a drive
rebuild. During a drive rebuild, limit I/O activity from the attached servers.
• After configuring the LUNs, remember to:
• Verify that all HBA connections to the MSA are recognized, including both paths in a
multipath configuration. Each time the MSA is power-cycled, all active connections to the
MSA are automatically detected and identified by their World Wide Port Name (WWPN).
As needed, manually add the additional connections. Run the ACU or CLI from each host in
the network to verify that each of its HBAs has been granted access to the MSA LUNs for that
host. If both connections are not granted access, I/O cannot fail over to the redundant path.
• Identify the operating system of each HBA connection to the MSA by setting the profile (also
called Host Mode) of each connection. For example, on Windows systems set the profile to
Windows.
• Limit access to the LUNs to prevent unintended or unauthorized access. Although not
required, HP strongly recommends this security measure. These settings are especially
important in heterogeneous environments to prevent the same or different servers running
different operating systems, and using a mix of HBAs from different vendors, from accessing
the same LUN. For each HBA connection, indicate the LUNs that it can access. In the ACU,
enter Selective Storage Presentation (SSP) settings and, in the CLI, build Access Control Lists
(ACL).
• In active/active multipath configurations, HP recommends disabling host-based Fibre
Channel HBA load balancing. By default, MSA firmware balances the LUNs between the two
MSA controllers. (Or optionally, you can manually specify the preferred controller path for
each LUN.) If HBA load balancing is also enabled at the host, the host instructions will
override the MSA instructions, resulting in additional processing time and reduced
performance.
• In Windows environments, HBA load balancing is set in the HP MPIO DSM Manager.
• In Linux environments, HBA load balancing is set via a driver command line option.
• Distribute ownership of the LUNs between the two MSA controllers in active/active multipath
configurations. Choose one of the following:
• Automatic load balancing (Default)—MSA firmware initially assigns ownership of all
LUNs to one of the two MSA controllers, and then automatically re-assigns LUN
ownership evenly between the controllers based on I/O loads of the LUNs.
• Manual load balancing—Through the ACU or the CLI, indicate the preferred path
(controller ownership) for each LUN. This method is recommended for environments that
are load balancing from the host.
HP StorageWorks 1500 Modular Smart Array installation guide 23