With the emergence of PCIe 3.0 systems, the need for a higher performance storage interface is critical. 12Gb/s SAS storage architectures offers the best bandwidth utilization of the PCIe 3.0 host bus. The PCIe 3.0 bus increases the maximum available bandwidth to 8,000MB/s, while 6Gb/s SAS is limited to 4,800MB/s, not using almost half of the potential throughput. The chart in Figure 1 shows that a 100% gain in storage throughput can be achieved by moving to a PCIe 3.0 system and using 12Gb/s SAS as the storage connection. 12Gb/s SAS actually provides more bandwidth than PCIe 3.0, providing a path to future performance enhancements. 12Gb/s SAS not only unlocks the bandwidth capabilities of PCIe 3.0, but also opens the door for extremely high small block performance well in the excess of 1M IOP/s.
In many solutions, systems can take advantage of the additional performance provided by 12Gb/s SAS without 12Gb/s storage devices by using optional bandwidth aggregation techniques. These techniques buffer between the lower performance devices (3Gb/s and 6Gb/s) and the 12Gb/s infrastructure. This offers beneficial bandwidth with legacy devices. Large datacenters with hundreds of drives can take advantage of the added bandwidth even when using 6Gb/s devices. Even nominally sized DAS installations with 20-30 drives can benefit from the performance gain. This performance level will be needed to support architectures using SSDs.
The “No Compromise” Performance: 12Gb/s SAS Designs Underway demonstration at the SCSI Trade Association (STA) Technology Showcase in May 2012 confirmed that 12Gb/s SAS is here today and performing to expectation. The demonstration topology shown in Figure 2 clearly highlights the performance level that can be achieved with 12Gb/s SAS using 6Gb/s and even 3Gb/s SAS and SATA drives. 12Gb/s SAS preserves the investment in storage while improving overall system performance, without the need to wait for the availability of 12Gb/s SAS devices.