History 2005: Microsoft and Samsung Launch “Flashy” HDDs

At Microsoft’s Windows Hardware Engineering Conference in Seattle, WA, at the end of April, a prototype of a strange device called Hybrid Hard Drive was exhibited. This was the first time a hard disk drive integrating flash as intermediary cache memory in the same standard ATA box had ever appeared.

It would seem a terrific idea to achieve both the benefits of magnetic storage for capacity and non-volatile solid state for speed and low power.

The prototype uses a 128MB NAND-based flash memory that can be used as a read or write buffer, not only to boot faster with the first logical blocks of the OS off the flash, but also to economize energy and spin down the rotating device the majority of the time.

Jack Creasey, Microsoft’s program manager at the hardware innovation group, estimates that an 80% gain in power can be achieved, since the spindle motor is kept in idle mode almost all the time. In fact, if the flash buffer allows it, all writing is automatically sent to the fast solid-state memory. The disk drive rotates only when the flash is full, and it needs to be emptied.

To a certain extent, the disk drive works as a backup of the flash memory working as a cache.

At the same time, with optimized handling of the exchange between the 2 memories, it’s possible that the read demand occur directly on the flash, and therefore more quickly, by avoiding the seek and rotational latencies of the Winchester unit.

The magnetic memory is taxed as seldom as possible, which can only prolong its life expectancy. What’s more, if by chance the computer suffers a shock when the disk drive isn’t in use, there’s a greater chance it will be unharmed after the incident.

The disk drive is one of the most fragile components of a computer, since it is the lone electro-mechanical device. This hybrid unit is designed to work with Longhorn, the next Windows OS from Microsoft, which provides for a new advanced memory management for caching read data in the system DRAM, but not write data, written instead to this very Hybrid Disk.

HDD and flash maker Samsung, designer of the prototype, expects to begin shipping the unit in substantial quantities via its HDD division in late 2006, the period when Longhorn’s arrival is expected.

Samsung Semiconductor, together with Seoul National University (SNU) developed the “proof of concept” Hybrid Hard Drive emulator prototype. For the moment, this interesting device is only planned for notebook computers by Microsoft, in order to improve the life expectancy of the batteries, although it seems to us impossible to imagine this at the moment, for desktop or especially enterprise critical applications that cannot be satisfied by frequent reboots of the magnetic device.

Can this idea from Microsoft and Samsung succeed? The advantages are obvious in terms of rapid read-write I/Os, of reliability and power consumption. With one slight downside nevertheless: when the data to be read are not in the flash cache, or when the latter is full, the rotating magnetic disk must be spun-up, which takes more time than a direct read-write operation on disk.

Hybrid Disks will cost more than conventional HDDs, since solid-state memory must be added. OEMs are rarely used to seeing the price of their HDDs increase. It’s not surprising that Samsung, one of the only disk drive makers (with Toshiba) also in NAND flash chips (and WW leader in this market) should be eager to work on this technology, while its competitors will be obliged to buy the flash components at a much higher price.

Yet, until now, that hasn’t prevented Hitachi and Seagate from working with Microsoft on the specs of a new ATA command set for the Hybrid Disk.

For the moment, only software company Microsoft is committed to the new idea, and only for its forthcoming Longhorn, but its power alone is enough to make the technology catch on, and oblige future versions of Unix, Linux or MacOS to add the management of these Hybrid Disks.

More worrying for the disk drive industry, is seeing flash memory infiltrate these units at all. More and more, with falling costs, the capacity of solid-state memory can be increased. To such a point, though, where magnetic memory may gradually disappear, to become relegated to the role of tape, as a secondary backup?

Another recent announcement from Samsung also gives food for thought in this domain. It’s a SSD based on 4Gb or 8Gb flash chips for a capacity of 4GB to 8GB in a 1.8-inch form factor, and 8GB to 16GB in the 2.5-inch volume, all of them with ATA interface.

The advantages, according to Samsung compared, over the HDD: lower power consumption, less than half the weight of a comparable sized HDD, no moving parts and thus greater reliability, minimal noise and less heat emission, better performance with a transfer rate of 57MB/s in read mode and 32MB/s in write mode. Disadvantages, as far as we can tell: smaller capacity and above all much greater price, although the exact figure has not been disclosed.

These novelties are relatively comparable to flash PC cards, but with an ATA disk interface. The SSD or RAM disk market is a very old one that dates back to the age of mainframes for critical applications, as a fast cache memory between HDDs and the computer, products once offered by IBM, StorageTek, MTI or EMC. But it was always a niche market, since the performance of HDDs always advanced, while SSD memories of the SDRAM sort were always decisively more expensive, requiring in addition a special battery in order not to lose the data on the volatile memory, as well as a disk drive to back them up. Companies working in this sector, including BitMICRO Networks, Cenatek, Curtis, Dynamic Solutions International, Simpletech, Solid Data Systems, Texas Memory Systems and TiGi, never became huge multinationals, and their offerings addressed only very critical applications in terms of performance. Some of them, such as BitMICRO Networks and Simpletech, as well as M-Systems, Memtech, SanDisk or Silicon Systems offer, like Samsung, flash disks based on non-volatile but slower solid-state memories.

Yet here again, the market is fairly narrow, limited to industrial or military applications. It will take several years before we see solid-state memories unseat HDDs, given the significant difference in the price-per-megabyte, where the former can only compete at low capacities, although the trend will eventually favor them, since their prices are currently falling at a faster rate than those for magnetic memories. Non-volatile solid-state memories have every advantage but one, a deal-breaker: price.

This article is an abstract of news published on issue 209 on June 2005 from the former paper version of Computer Data  Storage Newsletter.

Note: Finally, the concept of hybrid HDDs never succeeds after also being promoted by Seagate, Toshiba and WD.