HP 273914-B21 HP Smart Array Controller technology, 3rd edition - Page 6

• 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 2 of 6 Gb/s is double the SAS-1 transfer rate. SAS-2 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 cClass enclosure.3 For an up-to-date listing of HP Smart Array controllers that support the SAS-2 specification, see the Smart Array controller matrix: www.hp.com/products/smartarray 2 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. 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 6