Camarillo, Calif.--June 23, 1997--Vitesse Semiconductor Corp. (Camarillo, Calif.) announced the VSC7122, a full-speed Fibre Channel, Quad Port Bypass Circuit.
The VSC7122 is specifically designed for high-performance, high-data availability Fibre Channel Arbitrated Loop (FC-AL) RAID subsystems. The VSC7122 combined with Vitesse's VSC7120 Repeater Circuit form the necessary core building blocks for a designer to implement easily and then bring to market a Fibre Channel RAID subsystem.
FC-AL RAID subsystems are commonly implemented using a simple JBOD architecture in which the Host Adapter provides RAID functionality. The VSC7122 enables this type of design. The JBOD acts as an intelligent FC-AL router which ensures high data availability and hot swapability of disk drives.
Unlike traditional RAID controllers, the JBOD does not have a Controller/CPU/Memory Buffer, but uses the advanced features of FC-AL drives to provide high-end RAID performance.
The VSC7120 and VSC7122 chip set can be used in either active or passive JBOD backpanels. An "Active Backpanel" is JBOD implemented with all the ICs on the backpanel, allowing easy layout and low cost.
In systems where fault tolerance is of primary importance, a "Passive Backpanel" is implemented. This consists of two hot swapable cards--one for each loop--so that a failure of an IC does not affect the operation of the other loop.
Disk array drive resiliency is accomplished through an external Port Bypass Circuit controlled by a disk drive signal. To avoid attempted inclusion of failed or missing drives in the loop, the VSC7122 connects the drive to the Arbitrated Loop only if the disk drive indicates it is present and functioning properly.
The JBOD uses the VSC7120 Single Node Repeater to amplify the incoming signal and remove jitter at the JBOD subsystem input level so a clean signal is available to the disk array.
The VSC7122 is pin compatible with Vitesse's VSC7121; however, the VSC7122 offers improved output drive, which is especially useful in passive backpanels.
The device minimizes jitter accumulation by using fully differential circuits and providing symmetric rise and fall times. Integration reduces transmission-line effects due to impedance mismatches and cross talk, resulting in less skew between signal lines, lower pin counts, and reduced costs.
The VSC7122 is available in an industry-standard 44-pin, 10-mm PQFP package. It operates off a single 3.3-V supply and dissipates only 500 mW. Pricing for 10,000 units is $9.95, and samples are available now.
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