Compellent plans 900GB 2.5-inch disk drives Compellent's hardware road map shows larger capacity and faster 2.5-inch drives coming. The C-Drive conference was told that 900GB 2.5-inch drives spinning at 10,000rpm lay in the relatively near future. A 15K rpm 2.5-inch drive with 300GB capacity is coming too. This would be the fastest small form factor disk drive available …
and not really in context, but currently SSD are expensive and traditional mechanical drives are cheap, (in relation). So why not have the current the volatile cache backed up to, (in background by the drives processor), to a small SSD, which in turn is then copied to a mechanical HDD platter for those bits of the disk which arn't accessed as much?
Most cache is not volatile by virtue of redundancy to some degree or another in most enterprise class systems, but the idea of leveraging SSD as a form of cache is actually quite a good idea. As long as it is cheaper than D-RAM and faster than spinning disk, maybe it belongs in the middle in some way or another. As a PCI card, or as a storage device.
Apart from the cache volatility bit, which isn't the issue here. Note that SSDs also sport cache(!) If non-volatile cache is what you want, there's a thing called a rechargeable battery that does this without all that tedious fannying about with SSDs and cache copy algorithms.
What you've just described is what most, if not all, the enterprise storage vendors offer, a tiered solution with both rotating disk and SSDs. The more frequently accessed data is held on the SSD's for performance as SSDs have no stroke/latency overhead on Read and Update operations. The disk controller handles the migration of data between the conventional disk and the SSDs transparently.
What would be bloody sexy is if someone implemented a storage driver for PCs to do this automagically, so you could plug in a small SSD and a big disk and present 'em as one device. MS got part way there with ReadyBoost in Vista, but they FAILed big time (surprise) by restricting its use to USB "thumb" drives, so the I/O throughput loss here neatly offsets the seek gains. I reckon this could be the next "must have" on enthusiast mobos, replacing / supplementing RAID.
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