External Sas Port And Split Backplane - IBM Power 720 Overview

Supported RAID functions
Base hardware supports RAID 0, 1, and 10. When additional features are configured,
Power 720 and Power 740 support hardware RAID 0, 1, 5, 6, and 10:
RAID 0 provides striping for performance, but does not offer any fault tolerance.
The failure of a single drive results in the loss of all data on the array. This version
increases I/O bandwidth by simultaneously accessing multiple data paths.
RAID 1 mirrors the contents of the disks. The contents of each disk in the array are
identical to that of every other disk in the array. This version provides data resilience in the
case of a drive failure.
RAID 5 uses block-level data striping with distributed parity.
RAID 5 stripes both data and parity information across three or more drives. Fault
tolerance is maintained by ensuring that the parity information for any given block of data
is placed on a drive that is separate from those that are used to store the data itself. This
version provides data resiliency in the case of a single drive failing in a RAID 5 array.
RAID 6 uses block-level data striping with dual distributed parity.
RAID 6 is the same as RAID 5 except that it uses a second level of independently
calculated and distributed parity information for additional fault tolerance. RAID 6
configuration requires N+2 drives to accommodate the additional parity data, which makes
it less cost effective than RAID 5 for equivalent storage capacity. This version provides
data resiliency in the case of one or two drives failing in a RAID 6 array.
RAID 10 is also known as a striped set of mirrored arrays.
It is a combination of RAID 0 and RAID 1. A RAID 0 stripe set of the data is created across
a two disk array for performance benefits. A duplicate of the first stripe set is then mirrored
on another 2-disk array for fault tolerance. This version provides data resiliency in the case
of a single drive failure and may provide resiliency for multiple drive failures.

2.8.2 External SAS port and split backplane

This section describes the external SAS port and split backplane features.
External SAS port feature
The Power 720 and Power 740 DASD backplane (FC EJ01) offers an external SAS port:
The SAS port connector is located next to the GX++ slot 2 on the rear bulkhead.
The external SAS port can be used to connect external SAS devices (FC 5886 or
FC 5887), the IBM System Storage 7214 Tape and DVD Enclosure Express (Model 1U2),
or the IBM System Storage 7216 Multi-Media Enclosure (Model 1U2).
Note: Only one SAS drawer is supported from the external SAS port. Additional SAS
drawers can be supported by SAS adapters. SSDs are not supported on the SAS drawer
connected to the external port.
Split DASD backplane feature
The Power 720 and Power 740 DASD backplane (FC 5618) supports split drive bay
(FC EJ02). If FC EJ02 is configured, then the six small form factors (SFFs) slots are split into
a pair of three drive bay groups (3x3).
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IBM Power 720 and 740 Technical Overview and Introduction