SAS subsystem configuration that uses a two-way split backplane

This topic provides rules and examples of a configuration that uses a two-way split backplane.

The following rules apply to this configuration:

• Each SAS adapter can recognize only three of the disk drives and cannot function in dual storage I/O adapter (IOA) or high availability (HA) RAID mode. One SAS adapter connects to D1, D2, and D3. The other SAS adapter connects to D4, D5, and D6.
• The SAS adapters can be assigned to separate partitions for boot devices.
• This configuration supports disks without RAID (referred to as JBOD) or RAID drives. However, RAID drives are limited to three drives and no write cache.
• RAID 10 with two drives is limited. A RAID 10 array with two drives is equivalent to RAID 1 (mirrored drives). A RAID 0 disk array with one drive is similar to JBOD support. A RAID 10 array with one or three drives is not allowed.
• Solid-state drives (SSDs) and hard disk drives (HDDs) can be used, but they can never be mixed in the same disk enclosure.
• SSD and HDD can both be present in a split backplane if each side of the split backplane has only SSD or HDD.

Example: Two-way split backplane

This example shows a two-way split backplane configuration. Each embedded SAS adapter controls three disk drives.

Figure 1. Disk bays controlled by each embedded SAS adapter in a two-way split backplane

The following table lists the details of the two-way split backplane configuration.

Table 1. Configuration details

Embedded SAS adapter	Configuration details
Embedded SAS adapter A	The SAS adapter connects to disk drive D1, D2, and D3. Physical connections to the SAS cable are disabled. If the external SAS port is installed, it is not functional. The SAS adapter reports CCIN 57C7.
Embedded SAS adapter B	The SAS adapter connects to disk drive D4, D5, and D6. Physical connections to the SAS cable are disabled. If the external SAS port is installed, it is not functional. The SAS adapter reports CCIN 57C7.