Just a test For Jason
The basic fibre channel loop architecture limits the number of devices to 128. As the number of devices on the fibre channel loop increases, the challenge increases to provide scalable performance to all devices as they compete for communication resources. To reduce this resource starvation while increasing array sizes to their maximum, Xyratex has developed a product referred to as SBOD (Switched Bunch of Disks). This product is designed to be a plug and play replacement for existing Fibre Channel JBOD (Just a Bunch of Disks) technology, with much better RAS and performance capabilities.
The SBOD device includes an internal cross-bar switch to provide device communication while simulating the presentation of all FC-AL devices connected to it. This reduces the number of hops required for host-to-device communication, thus creating an almost host-to-device direct communication path. Another unique feature of the SBOD is the ability to ‘trunk’ two FC links within on simulated FC-AL loop such that inter-enclosure effective loop bandwidth is doubled. Through the elimination of the “physical loop” architecture, each and every node in the system is connected via a dedicated link, allowing full error management and diagnostics to be applied without disruption to the remainder of the devices in the “logical” loop. This enables vastly improved reliability and serviceability.
In summary, the data shown by the actual results is consistent with those results predicted by previous theoretical models. The performance using SBOD devices with “trunking” technology is highly consistent and shows no significant degradation in performance until loop saturation limits are achieved. The non-blocking nature of the SBODs allows concurrent initiator access to the “logical” loop demonstrating total throughput to peak at 1,550 MB/s, while the maximum performance in an equivalent JBOD configuration peaks at 384MB/s.
Results using a simulated SPC1-type workload, which typically include 8KB block transfers and a highly random access workload, shows how the loop performance effects start to influence the results in a standard JBOD configuration with a larger numbers of drives. This behavior is eliminated by Xyratex’s SBOD technology.
Attempts to explore the upper limits for the IOPs performance of this technology, using 512Byte data transfers have been hampered by CPU and other limits in the host systems. Peaks of over 200K IOPs have been achieved on SBOD configurations equivalent to twice that seen with JBODs. Xyratex believes with further host-side tuning that these limits can be overcome and significantly increased.
See more @ http://www.xyratex.com/technology/white-papers.aspx
