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Indeed there are good arguments today that in many situations SSD storage offers greater reliability and integrity than spinning disk.

Toshiba's PX02SMB160 is their current top of the range SSD drive at 1.6TB capacity, part of a family that also includes 800GB, 400GB and 200GB models. Only a couple of years ago the idea of a 1.6TB SSSD device would have seemed unthinkable - or at least unthinkably expensive. Now we see a world in which the comparative prices of SSD and HDD are coming ever closer together. Indeed the whole pricing discussion has evolved for many users from one of 'cost per GB' to one of 'cost per IOPS'. It is in this environment that the PX02SMB160 excels.

The drive uses multi-level cell (MLC) NAND rather than the dearer SLC NAND which has been more often found in earlier 'enterprise flash' offerings. SLC is usually held to offer higher data integrity and therefore be better suited to the enterprise. Toshiba claim that its innovative SSD controller on the PX02SMB160 gives the right combination of high performance and endurance, along with the economies of MLC.

It will handle up to 10 full drive writes per day, which should make it more than adequate for mixed workload read/write environments. The drive has been very cleverly designed to exploit the combination of MLC NAND and the new controller, and includes twice the amount of NAND modules (32) as Toshiba's first generation SSD offerings. The potentially higher error rates of MLC NAND are addressed by Toshiba's proprietary 'Quadruple Swing-By Code' (QSBC) which offers advanced error correction - and therefore higher endurance - for read-centric applications. The PX02SMB160's advanced error correction also includes what Toshiba call 'background patrol', a function to check data integrity and correct errors as they occur. This works alongside conventional wear levelling, which equalises program/erase cycles across the NAND. The blistering dual-port SAS-3 interface offers a data rate of up to 12GB/second.

The PX02SMB160 enterprise SSD provides 16 channels of NAND flash memory interfaces, twice as many as the Toshiba client SSD. The PX02SMB160 has an interleaved memory access architecture in which each channel is associated with two or more NAND flash memory chips (each with 8-Gbyte capacity). This means that while one memory chip is reading data from or writing data to memory cells, the controller can perform a data transfer with another memory chip simultaneously.

The increased concurrency among NAND flash memory chips not only compensates for the (relatively!) slow read and write speeds of the MLC NAND but also improves the overall SSD access performance. Furthermore, each NAND flash memory interface has a 1-to-2 multiplexer to double the number of accessible NAND memory devices. These design techniques combine to offer the 'Holy Grail' for enterprise storage: a high storage capacity of 1.6 TB combined with high performance.

What Toshiba have done so well with the PX02SMB160 is not just in the SSD NAND itself, but in designing the board and controller so as to optimise the whole drive for performance, endurance, and cost-effectiveness in the data centre.

Product: PX02SMB160 Enterprise SSD
Supplier: Toshiba Storage Products Division
Tel: 00800 84685463
Web site: toshiba.semicon-storage.com/eu/product/storage-products.html
Email: spdinfo@tee.toshiba.de