You can increase availability using multi-initiator and high availability to connect multiple controllers to a common set of disk expansion drawers.
The terms multi-initiator and high availability (HA) refer to connecting multiple controllers (typically two controllers) to a common set of disk expansion drawers for the purpose of increasing availability. This is commonly done in either of the following configurations:
An HA two-system configuration provides a high-availability environment for system storage by enabling two systems or partitions to have access to the same set of disks and disk arrays. This feature is typically used with the IBM® PowerHA™ for AIX®. The IBM PowerHA for AIX software provides a commercial computing environment that ensures that mission-critical applications can recover quickly from hardware and software failures.
The HA two-system configuration is intended for using disk arrays. The disks must be formatted to 528 bytes per sector. Any RAID level, or combination of RAID levels, can be used.
Use of disks without RAID (referred to as JBOD) is also possible. The disks must be formatted to 512 bytes per sector. This JBOD alternative is supported only on particular controllers and requires unique setup and cabling. See Installing an HA two-system JBOD configuration.
An HA single-system configuration provides for redundant controllers from a single system to the same set of disks and disk arrays. This feature is typically used with multipath I/O (MPIO). MPIO support is part of AIX and can be used to provide a redundant IBM SAS RAID controller configuration with RAID protected disks.
When using an HA single-system configuration, the disks must be formatted to 528 bytes per sector and used in one or more disk array. Any RAID level, or combination of RAID levels, might be used. Disks formatted to 512 bytes per sector are not supported in an HA single-system configuration.
Not all controllers support all configurations. See the feature comparison tables for PCIe and PCI-X cards to look for controllers that have HA two-system RAID, HA two-system JBOD, or HA single-system RAID marked as Yes for the configuration that you want.
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