HP ProLiant AMD-based 100-series G7 servers
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HP Smart Array and SAS/SATA technology
The newest serial PCIe 2.0-capable Smart Array controllers use SAS technology, a point-to-point
architecture in which each device connects directly to a SAS port rather than sharing a common bus
as parallel SCSI devices do. Point-to-point links increase data throughput and improve the ability to
locate and fix disk failures. More importantly, SAS architecture solves the parallel SCSI problems of
clock skew and signal degradation at higher signaling rates.
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The latest Smart Array controllers are compatible with SATA technology and include the following
features to enhance performance and maintain data availability and reliability:
SAS and SATA compatibility — SAS-2 compliance lets administrators deploy and manage both
SAS arrays and SATA arrays. Smart Array configuration utilities help administrators configure
arrays correctly so that data remains available and reliable.
SAS wide port operations — Wide ports contain four single lane (1x) SAS connectors and the
cabling bundles all four lanes together. SAS wide ports enhance performance by balancing SAS
traffic across the links. 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 tolerance for link
failures is possible because wide port connections are established from Phy
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to Phy, and multiple,
simultaneous connections to different destinations are possible. The most common use of these 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 — Low-cost, high-speed switches called expanders can combine multiple single
links to create wide ports and increase available bandwidth. SAS expander devices also offer
higher system performance by expanding the number of hard 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. For more information on the HP SAS Expander Card, go to
http://h18004.www1.hp.com/products/servers/pr
oliantstorage/arraycontrollers/sas-
expander/index.html.
SAS-2
SAS-2 and PCIe 2.0 are a
mong the technologies responsible for a significant increase in performance
over past generations of Smart Array controllers. The second-generation SAS (SAS-2) link speed
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of
6.0 Gb/s is double the SAS-1 transfer rate. Operation at SAS-2 link speeds requires SAS-2 compliant
hard 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 is also backward compatible with SAS-1.
Beginning with HP product releases in the first quarter of 2009, Smart Array controllers are SAS-2
capable. In fully supported controllers, 6-Gb/s SAS technology allows Smart Array controllers to
deliver peak data bandwidth up to 600 MB/s per physical link in each direction. SAS devices are
capable of sending and receiving data simultaneously across each physical link (full duplex mode).
When running full duplex, 6-Gb/s SAS technology can deliver peak data bandwidth up to 1200
MB/s.
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For more information about SAS technology, refer to the HP technology brief titled “Serial Attached SCSI storage technology”
available at http://h20000.www2.hp.com/bc/docs/support/SupportManual/c01613420/c01613420.pdf
.
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The mechanism that contains a transceiver which electrically interfaces to a physical link. Phy is a common abbreviation for
the physical layer of the OSI model.
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The Serial Attached SCSI - 2 (SAS-2 or SAS 2.0) is a draft standard, and is the product of the Technical Committee 10t
Organization. SAS 2.0 is second generation of SAS and is based upon SAS - 1.1. The SAS-2 specification is available from
the 10t website,
http://www.t10.org.