Technology and architecture of HP ProLiant AMD-based 100 - series G6 (Generation 6) servers

• SAS wide port operations — Wide ports contain four single lane (1x) SAS connectors and the

cabling has all four lanes bundled 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 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/proliantstorage/arraycontrollers/sas-expander/index.html.

SAS-2 standard

The second-generation SAS (SAS-2) link speed

of 6 Gb/s is double the SAS-1 transfer rate. SAS-2

link speeds require 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 connections have the potential to deliver peak raw data bandwidth of up to 600 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. Actual

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

connections. The SAS-2 standard is compatible with both Serial SCSI and Serial ATA protocols for

communicating commands to SAS and SATA devices. SAS-2 compliant controllers are fully

compatible with 1.5 Gb/s and 3 Gb/s SATA technology.

For the most up-to-date listing of HP Smart Array controllers that support the SAS-2 specification, see

the Smart Array controller matrix:

http://www.hp.com/products/smartarray

Battery backed write cache

he battery backed write cache (BBWC) is required for capacity expansion (adding one or more

physical disks to an existing array). The controller recalculates parity and balances the data across all

the disks. During the expansion, the BBWC preserves data and logical structures on the array. The HP

650 mAh P-Series battery extends battery life up to 48 hours before recharging is necessary.

NOTE:

In the ProLiant DL165 G6 server, the Smart Array P212 controller cache size is limited

to 256 MB

Zero Memory RAID

Using Zero Memory RAID (ZMR), administrators can create a RAID 0-1 configuration without

additional memory. ZMR uses memory embedded in the controller, approximately 1K in size, and

Serial Attached SCSI-2 (SAS-2) is an American National Standards Institute (ANSI) standard from the INCITS T10 Technical

Committee on SCSI Storage Interfaces. SAS-2 is the successor to SAS-1.1 and SAS-1.