Sas-2 Standard - HP 273914-B21 - Smart Array 6404/256 RAID Controller Technology Brief

• SAS wide port operations — Wide ports contain four single lane (1x) SAS connectors and the
cabling bundles all four lanes together. SAS wide ports allow balanced SAS traffic distribution
across the links for enhanced performance. In addition, wide ports provide redundancy by
tolerating up to three physical link failures while maintaining the ability to communicate with the
disk drives. The most common use of wide links is to a JBOD or to an internal server expander
connecting to large numbers of drives. No special configuration is required for this functionality.
• SAS expanders — SAS expander devices offer higher system performance by expanding the
number of disk drives that can be attached to an HP Smart Array controller. SAS expanders are an
aggregation point for large numbers of drives or servers providing a common connection. By
cascading expanders, administrators can chain multiple storage boxes together.
The full height, HP Serial Attached SCSI (SAS) expander card supports up to 24 internal drive bays
plus an external connection for tape. The HP SAS Expander Card is well suited for ProLiant server
customers that want to use RAID with more than eight internal disk drives. With the SAS expander
installed between the drives and the controller, users will see the same performance characteristics as
if the drives were connected to JBOD. For more information on the HP SAS Expander Card, go to
http://h18004.www1.hp.com/products/servers/proliantstorage/arraycontrollers/sas-expander/index.html

SAS-2 standard

The second-generation SAS (SAS-2) link speed
link speeds require SAS-2 compliant disk drives. SAS-2 eliminates the distinction between fanout and
edge expanders by replacing them with self-configuring expanders. SAS-2 enables zoning for
enhanced resource deployment, flexibility, security, and data traffic management.
SAS-2 connections have the potential to deliver peak raw data bandwidth of up to 600 megabytes
per second (MB/s) per physical link in each direction. SAS-2 devices are capable of sending and
receiving data simultaneously across each physical link, which is known as full duplex. When
effectively implemented, full duplex, 6 Gb/s SAS connections can deliver peak raw data bandwidth
of up to 1200 MB/s between the controller and storage device. It is important to note that the SAS-2
data bandwidths described here are theoretical speeds identified by the SAS-2 standard. Real world
performance will be affected by the performance of storage devices attached to the SAS-2
connection.
Smart Array controllers, with releases beginning in the first quarter of 2009, incorporate SAS-2
capable performance and features. The SAS-2 standard maintains compatibility with both Serial SCSI
and Serial ATA protocols for communicating commands to SAS and SATA devices. SAS-2 compliant
controllers are compatible with present generation 3Gb/s SATA & 6Gb/s SAS as well has
backwards compatible with past generation SATA & SAS devices.
The Smart Array P700m controller supports SAS-2 zoning capabilities. SAS-2 zoning uses a shared
SAS fabric to assign multiple servers to multiple storage devices within a rack. HP presently employs
SAS-2 zoning in the HP 3Gb SAS BL Switch & MDS600 drive enclosure solution with the Smart Array
P700m. This allows the creation of a group of up to 100 drive bays across four MDS600 drive
enclosures. The group of drive bays can then be electronically assigned to any server within the c-
Class enclosure.
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For an up-to-date listing of HP Smart Array controllers that support the SAS-2 specification, see the
Smart Array controller matrix:
Serial Attached SCSI-2 (SAS-2) is an American National Standards Institute (ANSI) standard from the INCITS T10 Technical
2
Committee on SCSI Storage Interfaces. SAS-2 is the successor to SAS-1.1 and SAS-1.
3 For more information on BladeSystem Direct Connect SAS configurations, go to
http://www.hp.com/hpinfo/newsroom/press_kits/2009/convergeeverything2009/DataSheetDirectconnectSASstorageforHPB
ladeSystem.pdf
of 6 Gb/s is double the SAS-1 transfer rate. SAS-2
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www.hp.com/products/smartarray
.
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