Original URL: http://www.theregister.co.uk/2010/05/14/hybrid_sshd_kerekes/

Will hybrid SSD/HDD products succeed?

Solid products or flash in the pan?

By Chris Mellor

Posted in Storage, 14th May 2010 09:01 GMT

Comment Toshiba is mulling over a combined flash drive and spinning disk product. Will such a hybrid SSHD succeed or is it doomed to fail?

Zsolt Kerekes of StorageSearch, who follows the SSD market closely, thinks it would fail if brought to market. He said: "I've always thought that 2.5-inch hybrids (SSD + HDD) were a waste of space - ever since the idea surfaced. It doesn't matter who makes them."

His reasoning is that "the volume market for these would be in enterprise arrays - but you get much better results by mixing and matching genuine SSDs and genuine HDDs with an ASAP SSD type of controller (or human tuning) and at much lower cost".

An ASAP controller is, literally, an As-Soon-As-Possible controller, a term used by Kerekes to signify a controller "which enables users to get usable speedups from (separate) SSD caches running in tandem with HDD arrays in minutes or hours without human hot spot tuning". The problem area is identifying data hot spots quickly enough and moving them from the HHD component to the SSD component of the drive. ASAP controllers do this automatically.

An example of such a controller is Dataram's XcelaSAN.

Kerekes says that: "The mythical consumer market for earlier hybrids was killed by Vista. Nowadays notebook buyers can afford to buy 100 per cent SSDs - and if 3-bit MLC (multi-level cell) SSDs work the price/capacity slope will tip more in SSD's favor."

Currently 3-bit MLC has slower access speed and a shorter working life than 2-bit MLC which is, in turn, exceeded in speed and working life by single-level cell (SLC) flash. If suppliers can solve the 3-bit MLC issues this means that enterprise SSD buyers could and would, in his view, buy 3-bit MLC SSDs separately from hard disk drives. They would simply replace spinning drives with solid state drives for storing fast-access data.

Kerekes thinks one kind of hybrid drive will be popular: "On the other hand, what I call fat flash SSDs; flash with a massive RAM cache, are popular hybrids and do meet real needs for apps speed-ups." ®