Storage Configurations and Support
Network Storage is responsible for defining and supporting the configurations of host bus adapters and external storage
arrays in combination with drivers and storage management tools regardless whether the arrays utilize SCSI or FC
technology. These same components will influence the functionality available for the internal storage array as well.
FC-AL loops
Supported configurations require that individual FC-AL loops are connected only to a single type of array. However,
individual loops of a multi-loop controller i.e. X6727A, PCI to dual FC-AL controller, may be connected to different types
of arrays provided that all arrays on any individual loop are the same.
The external HSSDC connector is on the same loop as the internal disks. At this time, Sun does not support arrays
connected to the port.
Multipathing and Benefits
Multipathing provides two independent hardware connections to a disk or an array, whether internal or external. The
primary objective is to maintain accessibility to data even in the event of a hardware failure of the controller or cabling,
etc.
Multipathing may offer higher throughput and bandwidth to the disk array, but generally this is considered as a
secondary advantage.
Within a storage logical unit, RAID techniques may be applied for the purpose of masking the failure of an individual
disk. Typically, RAID 5, striping with distributed parity, is more effective than RAID 1, mirroring or complete, duplicate
copies.
Multipathing to the Internal Storage Array (with dual controllers)
The internal storage array is controlled via the embedded/integrated FC-AL controller, a Qlogic 2202 chip. The second
path may be implemented via the X6727A, PCI to dual FC-AL controller and the internal cable kit. This cable connects
the internal FC-AL port of the adapter to the secondary FC-AL loop connector on the disk backplane.
Multipathing to External Arrays (with dual controllers)
When implementing multipathing to external arrays with dual internal controllers, each path from the host must utilize the
same interface, i.e. two X6727A or two X6799A. The X6799A, PCI to single FC-AL controller, is considered equivalent
to the X6727A, PCI to dual FC-AL controller, as they are both implemented with the same Qlogic 2200 series chip. One
may be substituted for,or mixed with the other, when implementing multipathing to an external array.
Software Requirements to Implement Multipathing
In order for multipathing to be transparent to applications, an intermediate software level is required to provide a layer of
abstraction between the applications and the physical connectivity to the storage subsystem. This layer can mask the
failure of an individual loop from the application and redirect the I/O over the alternate path. All applications referencing
the abstraction layer pick up the failover capability without having to deploy specific code for path selection and recovery.
Important: Regardless whether multipathing to the internal array or an external array is desired, a software manager such
as Veritas Volume Manager with Dynamic Multipathing is required. Failure to utilize a volume manager may result in the
inadvertent corruption of the volume structure and/or content resulting from the unsynchronized access via two
independent paths to the same physical device.
To insure data integrity, Veritas Volume Manager with Dynamic
Multipathing must be implemented for multipathing to the internal array. Failure to do so will render the configuration
unsupported.
An unbundled enhancement after Solaris 8 7/01 referred to as Multiplexing I/O (MPxIO) will provide multipathing to
external arrays, the Sun StorEdge A5x00 and Sun StorEdge T3 arrays via the X6799 or X6727 PCI adapters. However,
this version will not offer support for the FC-AL loops upon which the boot device resides, i.e. most likely the internal
storage array. That functionality is planned for a subsequent version until which time, Veritas Volume Manager with
Dynamic Multipathing is required.
Sun Fire
TM
V480 Server
Sept. 26, 2002
Just the Facts
42
Sun Proprietary and Confidential - Internal Use Only
