Your next Windows laptop could run faster and last longer on a single battery charge thanks to a new generation of hybrid hard disk drives and a feature in the Windows Vista operating system that leverages NAND flash memory as a disk cache.
The feature, called ReadyDrive, could also reduce the incidence of hard disk crashes due to shocks" the most common hardware failure in notebooks" by decreasing the amount of time the disk needs to be spinning.
Notebooks will be the first systems to leverage the technology, but its potential is much broader, said Ruston Panabaker, an architect in Microsoft's Windows hardware innovation group. "We fully expect to see it show up in desktops and perhaps even in specific server applications," he said.
ReadyDrive has spawned a new category of flash-assisted hard drives. Both Samsung Semiconductor and Seagate Technology have announced hybrid drives that integrate a 1.5-in. magnetic hard disk with up to 256MB of onboard flash. Both are expected to be available early next year. A competing technology from Intel, code-named Robson, places the cache on the motherboard, along with a controller chip. Robson will launch with Intel's Santa Rosa notebook platforms in the first quarter of 2007.
"The interface to flash chips has been doubling in read and write performance every single year," Panabaker said. This year market research company IDC predicted that flash prices would drop by 55 percent. Halfway through 2006 prices have already exceeded projections. Current prices have dropped into the US$17.50 per GB range, and the trend is expected to continue.
Because disk I/O speeds haven't kept up with CPU horsepower gains, it was just a matter of time before storage vendors turned to flash. "Vista was certainly the catalyst," said IDC analyst John Rydning, but the use of hybrid drives could well expand beyond Windows systems.
A related Vista feature, ReadyBoost, is a read cache that allows Windows to cache memory pages that won't fit into main memory on a USB flash drive. Because the flash device could be removed at anytime, however, unique data cannot be stored on it and data is encrypted for security reasons.
Panabaker said, "The final solution is ReadyDrive," a write cache that can cache portions of the operating system to facilitate faster boot up and resume times. "I would expect to see a 30 percent boot time savings [using ReadyDrive]," he said. During normal operations, data retrieved from the cache will be transferred two to three times as fast as from disk, Panabaker said. Samsung claims that the cache in its hybrid drive is 50 times faster than disk.
Not all applications will benefit equally from hybrid disks, however. The biggest performance improvement comes from faster seek times" the time it takes to locate data on disk. Those latencies, more than transfer rates, tend to be the bottleneck. Therefore, some applications that read sequential strings of data" such as video" won't see as much be
Windows, however, is more transactional. It tends to trickle log files and other data even when systems are idle, keeping drives spinning. Placing that data in the write cache allows disk drives to power down. That could reduce power consumption by up to 90 percent in some cases and increase usable system life by 8 percent to 12 percent, said Don Barnetson, director of flash marketing at Samsung Semiconductor.
Hybrid disk drives will also be more reliable. "The hard disk drive is able to withstand shocks when it's in an off state. We can improve the reliability up to five times," he said.
While hard drive makers advocate a hybrid disk drive that places flash memory cache with the physical disk drive, Intel thinks the cache should be on the motherboard. Its Santa Rosa notebook platform will include 256MB of flash and can look like a ReadyBoost device or a hybrid disk accessible to ReadyDrive, said Kishore Rao, product line manager.
Panabaker said hybrid drives are a better design for ReadyDrive, since they keep the cache and disk under the management of the storage subsystem. "Microsoft has concerns about the issues associated with such a separated nonvolatile cache," Panabaker said.
"We don't see that as being an issue," said Kishore, adding that Intel's Matrix storage manager chip will safely handle all I/O operations. Disk drive makers say problems with flash on the motherboard will be harder to service, while Intel counters that the hard disk is more likely to fail, and when that happens the user must throw out the flash along with the disk.
"It's difficult to predict how this is going to play out with PC manufacturers," said Rydning at IDC. But users aren't likely to care, as long as computers that use the technologies perform and cost the same.
Jack Weilandt, chief technologist and director at NSTAR Electric & Gas, sees an 8 percent to 12 percent increase in battery life as "marginal at best," and added that faster boot times are mitigated by the fact that "more boot time is spent in authentication and managed desktop component loads than in the loading of Windows itself." But he said the durability of hybrid drives is attractive.
"The key feature to me is that the heads can stay locked for large amounts of time. We put laptops in trucks and carry them to work sites where they can get banged around quite a bit, so this technology would greatly reduce [hard drive damage]," Weilandt said, adding that a solid state disk would be even better.
Performance benefits may be the main reason for using hybrid disks in desktops, but Panabaker said some large enterprise customers have approached Microsoft and said that they'd like to have hybrid drives in desktops so the disk drives will spin down during periods of inactivity, cutting power consumption and heat generation.
The same power savings could be beneficial for servers with direct-attached storage, he said. Although Panabaker wouldn't confirm it, it is likely that ReadyDrive will be integrated into the next version of Windows Server. "The code is part of the core bits in Windows," he acknowledged.
The outlook for hybrid disk in networked storage is less clear. ReadyDrive doesn't support iSCSI network-attached storage, but Panabaker said he sees value in supporting it as a way for network storage devices to save power and generate less waste heat in data centers.
Chris Bennett, vice president of core systems at NetApp, said the technology might find a niche in very small network-attached storage systems, but sees "no apparent benefit" for enterprise class systems, noting that NetApp disk arrays already use faster DRAM caches and those systems typically are not powered down.
However, allowing drives to spin down during periods of inactivity could be important as data centers face heat and power issues. "In a server environment, power consumption is a big factor. If you can keep disk drives spun down that saves power," Rao said.
Falling prices for flash could make it more attractive for network storage, Panabaker said. "[Flash] is now cheaper than DRAM so we see an interesting trend where it may be cheaper in really specialized products, such as some high-end SCSI arrays, to use flash," he said.
As performance continues to climb and cost drops, flash is likely to become attractive for more and more applications. "Any place there is a gap between processor performance and disk I/O, flash will apply," Rao said.