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UBM Tech

A closer look at LSI’s MegaRAID SAS 9260CV-4i controller

Allan Yogasingam, UBM TechInsights -June 20, 2012

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Hardware RAID (redundant array of independent disks) controllers have been around for quite some time, growing in popularity with the rise in use of ATA hard drives. A crowded market, featuring products from companies such as Intel, Adaptec (now PMC), HP, and Promise, requires manufacturers of these types of cards to produce devices that will stand out against the rigorous testing and benchmarks set by users. In the relatively short history of RAID controllers, a changing of the guard took place when SAS and SATAs replaced parallel SCSI and PATA as the serial interfaces of choice. LSI’s MegaRAID SAS 9260CV-4i controller takes advantage of both the SAS and SATA interfaces to operate stably and offer high performance, the two biggest demands of its market.

The MegaRAID controller features the proprietary 800-MHz LSISAS2108 ROC (RAID-on-Chip), 512-MByte DDR2 cache memory, and a x8 PCI Express 2.0 host bus interface. Its strongest feature, however, is CacheVault technology, which uses NAND flash memory powered by supercapacitors to protect data stored in the MegaRAID controller cache. CacheVault technology claims to have a “greener” approach to cache protection, eliminating the need for the lithium-ion battery that traditional PCI-based RAID controllers require to protect DRAM cache memory.

In this controller, data is automatically written from the volatile DRAM cache to the NAND flash when a power failure occurs, while the charged supercapacitors keep current continuous during operation. Once power returns, the DRAM is recovered from the NAND flash, and the system experiences no loss of data. Based on CacheVault alone, you could see the appeal of MegaRAID controllers to IT workers everywhere.

The MegaRAID 9260CV-4i controller consists of three boards: a main board, which features the I/O of the controller; a daughterboard that houses the DDR2 SDRAM array; and the CacheVault power-module board, which is the heart of the CacheVault technology that distinguishes the MegaRAID controller from its competitors.

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The primary components of the CacheVault power-module board are AgigA Tech supercapacitors and a Cypress Semiconductor CY8C29466 programmable SOC. The Cypress SOC acts as a smart controller, while the four large capacitors are used in conjunction with this SOC to supply power in case of power failure. Cached information in the volatile SDRAM will be transferred to NAND flash before power is completely drained.

1. The daughterboard consists of numerous design wins from large-scale companies such as NXP, Analog Devices, Cypress, and ST Microelectronics. The notable devices on the front side of the board include Xilinx’s XC3S1400A Spartan-3A FPGA and four 4-Gbit NAND flash devices provided by Micron Technology.

Next page: Backside of daughterboard with Samsung memory and NXP DDR2 multiplexer

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