Hybrid hard drives: Can Samsung and Microsoft invent a new market for 2007?


Seattle (WA) - For the Windows Hardware Engineering Conference this May, Microsoft and Samsung Semiconductor are preparing the first demonstration of a self-contained, production-ready prototype for Samsung's hybrid hard drives, models of which will go into production before the end of the year, a Samsung official told TG Daily. These hybrid hard drives will represent the next stage of Samsung's ongoing project with Microsoft to expedite I/O throughput time by leveraging large OneNAND Flash memory caches to radically improve application performance, as well as reduce system power-up and power-down times to under one second.

To help catalyze rapid adoption of hybrid HDD technology by OEMs, TG Daily has learned, Microsoft explored as early as November 2005 the possibility of making hybrid HDD inclusion a requirement for builders of desktop and mobile systems for both consumer and business customers to qualify for the company's Premium logo for Windows Vista compliance, as soon as the second quarter of 2007. The Premium logo is granted by Microsoft to builders who have assured the company that they are providing users with, according to Microsoft, the "richest" computing experience currently available.

Officials from both Microsoft and Samsung declined comment on future Premium and Basic logo requirements. However, when Microsoft unveiled its partnership with Samsung on hybrid HDD technology in April of last year, its presentation indicated that Microsoft was moving toward considering "preferred storage platform" status for systems that included hybrid drives.

If Microsoft decides to continue or resume pursuing hybrid HDDs for is Premium logo requirements, it could represent one of the most concerted efforts by the company to significantly alter the fundamental architecture of PCs since its backing of Plug-and-Play. But it could also symbolize an unusual U-turn in the evolution of Microsoft's support strategy, by not just openly endorsing but mandating the inclusion in PCs of a component manufactured mainly, if not only, by one company.

A hybrid HDD utilizes a non-volatile cache of NAND Flash memory to store frequently accessed sectors of data, in order to leverage Flash's quick read times to make those sectors more readily accessible. In early demonstrations, Microsoft demonstrated 128 MB of Samsung's OneNAND cache, and recommended "as much as" that amount; indications are today that Samsung's working prototypes, to be revealed this April, could include much more, perhaps as high as 1 GB. Microsoft has explained the purpose and usefulness of this cache in a number of ways, but TG Daily has learned that those explanations - including some which parallel the functionality of L1 and L2 caches for a CPU - are not altogether relevant to current Samsung prototypes.

Don Barnetson, associate director of Flash marketing for Samsung Semiconductor, gave TG Daily a more current explanation: Samsung's hybrid drives utilize a broad storage map which incorporate both the Flash cache and the traditional platter space. But the Flash space is treated with greater preference, since its read times are faster. So frequently used sectors (note: not files) are mapped to the Flash space to increase performance. Furthermore, drivers in the operating system have certain authority to designate which sectors are given such preferential treatment.

"What you do is take a logical address of a hard disk drive - say, sector 0," Barnetson illustrated for us, "and rather than having it reside on magnetic media, you say it now resides on Flash media. Any operations that are done to it, whether they be read or write, are not so much cached as they are pinned, or physically moved from the magnetic media over to the Flash memory." A sector which contains frequently accessed files or other elements, such as a FAT table, could be pinned to Flash memory for faster read and write performance, he said.

Once a logical address is pinned to Flash, I/O requests to that address are automatically redirected to the cache. This is somewhat different from the dynamics of a memory cache, where elements of memory in the vicinity of the address currently being accessed are copied into the cache, since those other addresses in the neighborhood are the ones most likely to be addressed next. Once a memory address falls off the "page" in the memory cache, it's refreshed with the addresses in the same page of the next address. This is not at all how a hybrid HDD cache works, Barnetson was clear in illustrating. "Once you pin a sector, you just read and write to it as you normally would; it's just that the drives will respond more quickly," he stated.

Despite recent makeovers that give the company the veneer of a conventional consumer electronics manufacturer, Samsung is, first and foremost, a semiconductor company. So it is clearer now than ever that its entry into the hard drive market space in 2003 was a precursor to carving out a potentially huge market space for the expansion of one of its key existing businesses, NAND Flash memory. According to estimates from analyst firm iSuppli, Samsung remains the principal supplier of the world's Flash memory, with an estimated 50.4% market share in terms of revenue among the top seven suppliers, in Q4 2005. Only Toshiba, the #2 player by iSuppli's estimate with 19%, has the virtue of also being a hard drive manufacturer.

On its own, Samsung's value proposition for hybrid hard drives goes like this: By pinning to Flash sectors of data that are reserved for use in powering down or suspending the system, the time consumed in such everyday acts could be whittled down to a mere second or less. "Particularly on the power-down side," remarked Barnetson, "if the Flash cache is sufficiently large, you're able to have most of the hibernate files already pre-stored in Flash memory. So rather than having to write it out to the hard disk drive as is done in Windows XP, most of it can be there already, and you can power down the system fairly rapidly.

"On the resume side," Barnetson continued, "Microsoft is doing a lot of work with BIOS vendors to reduce the POST time." Today's power-up cycles, he explained, consist of the BIOS executing its Power-On Self-Test (POST) cycle at the same time the hard drive is spinning up to speed. Once both parallel cycles are completed, the system can finally start recovering its suspend file, for a total process consumption time of 20 seconds or more. "In the future, that POST time will be reduced to hopefully less than one second," he predicted. This is because future boot cycles will stream recovery data from the Flash cache at the same time the platters are coming up to speed.