HP BL260c Technologies in HP ProLiant G5 c-Class Server Blades - Page 10

x8 link has an effective bandwidth of 4 GB/s. This flexibility allows slower devices to transmit on a single lane with a relatively small number of pins while faster devices can transmit on more lanes as required.6 Figure 10. PCI Express bandwidth Link Max. bandwidth size (Send or receive) x1 250 MB/s x4 1 GB/s x8 2 GB/s Total Bandwidth (Send and receive) 500 MB/s 2 GB/s 4 GB/s A PCIe 2.0 device can be used in a PCIe 1.0 slot. For best performance, however, each card should be used in a slot that supports its logical link size. Serial Attached SCSI technology SAS is a serial communication protocol for direct-attached storage devices such as SAS and SATA Small Form Factor (SFF) disk drives. It is 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 high signaling rates.7 A battery-backed write cache (BBWC) is available as an option for the Smart Array controllers. The battery prevents information in the buffer from being lost in case of an unexpected system shutdown. In the case of a complete system failure, IT administrators can move the controller and disks to a different server where the controller will flush out the cache to the disks after power is restored. In the case of a controller failure, administrators can move the cache module and disks to a working controller where the cache will be flushed out to the disks. The battery will last up to two days without receiving any power from the computer. SAS and SATA Small Form Factor hard drives The SAS architecture enables system designs that deploy high-performance SAS and high-capacity SATA8 SFF drives. This capability provides a broad range of storage solutions that give IT managers the flexibility to choose storage devices based on reliability, performance, and cost. 6 For additional information about PCI Express technology, see the technology brief titled "HP local I/O technology for ProLiant and BladeSystem servers": http://h20000.www2.hp.com/bc/docs/support/SupportManual/c00231623/c00231623.pdf. 7 For more information about SAS technology, refer to the HP technology brief titled "Serial Attached SCSI storage technology": http://h20000.www2.hp.com/bc/docs/support/SupportManual/c01613420/c01613420.pdf. 8 For more information about these features, refer to the technology brief "Serial ATA technology": http://h20000.www2.hp.com/bc/docs/support/SupportManual/c00301688/c00301688.pdf. 10