Flash, Storage Vendors Eye Windows Vista
Flash, Storage Vendors Eye Windows Vista
SAN JOSE, Calif.Flash memory looks to give Windows Vista performance a helping hand next year. In presentations by Intel and Microsoft at the Flash Memory Summit conference here, the details of how that flash-enabled speed boost will be accomplished grew a bit more clear.
Some of the flash memory architectures may find their way into slots on logic boards of Intel-based Macintosh and Linux systems in 2007 as well as on forthcoming "hybrid" hard drives that incorporate large flash caches alongside their rotating platters.
Sharing the keynote address on Aug. 8 were Matt Ayers, Microsofts program manager of Windows Client performance, and Intel Scientist Knut Grimsrud, director of storage architecture for the Intel Storage Technologies Group. Each discussed the technological reason for the use of flash in forthcoming notebook and desktop systems as well as further details on the requirements of the flash architectures.
Ayers ran down the features of Windows Vistas ReadyBoost, which can take advantage of a connected flash cache to speed up overall system and application performance, and ReadyDrive, which uses a flash cache on the systems hard drive to improve boot times and power usage.
According to Ayers, Microsofts flash-based features due in Vista "provide a more consistent computing experiencethey actually make Vista run better."
The technologies are expressions of Microsofts SuperFetch intelligent memory management technology that will arrive in Vista. The software monitors what programs the user runs and when, and then makes sure that the necessary program resources are in memory at the required time, Ayers said.
"Theres no reason that an operating system cant get smarter and more efficient over time. It knows what you do and when you do them. It learns, basically," he said.
Ayers noted that the multiple seeks needed to fetch a resource from the hard disk can take as long as 60 milliseconds and these events quickly add up to long delays for the user. However, when these same resources are in a flash cache, the time can be less than a millisecond.
The SuperFetch technology will prioritize the cache and will even cut short tasks that run when the machine is idle, such as background maintenance tasks or security scans, in order to improve availability of programs and frequently used data.
The ReadyBoost flash cache will be both encrypted and compressed, he said. In addition, theres no unique data on the caches; everything that is in the cache is backed up on the systems hard drive. If the cache is removed or the system hibernates, the cache is rebuilt.
Ayers said Microsoft had expanded the list of flash media types supported by ReadyBoost, from USB 2.0 thumb drives to a range of other card types and interfaces, including Mobile PCI, Compact Flash and Sony Memory Stick.
To gain the ReadyBoost logo, the flash product will need to have a capacity of 512MB or greater; provide a throughput of 5MB per second for random 4K reads; and 3MB per second for 512K random writes. He said the flash will need to be from SLC (single-level cell) technology that offers more performance than the multilevel cell flash on the market.
However, users will be able to plug in a noncertified flash device with 233MB free and ReadyBoost will attempt to use it, Ayers said to eWEEK.com later during a demonstration of the technologies. In addition, ReadyBoost will test the device with a number of read and write cycles before each use.
For the flash cache embedded on the drive, ReadyDrive can operate as a write cache as well as read cache. Since its out of sight and difficult to remove, the cache is trusted by the system and its data is stored across state transitions such as boots suspend-and-resume cycles and hibernation.
"Since were buffering write data and read data, we can be a lot more aggressive about when we spin the drive down," Ayers said. This will make power performance more efficient and thus improve battery life, he said.
The minimum flash cache supported on drives will be 50MB, Ayers said, and Microsoft was pushing drive vendors for capacities of 128MB or greater. In addition, system vendors will be able to use a portion of the cache for tools, help files or other resources.
Next Page: Intels Robson technology and concerns about flash endurance.
Intels Robson technology
Intels Grimsrud presented findings from the companys work on its flash-based caching system called Robson. As demonstrated at the conference, Robson comprises a flash cache of up to 4GB, a controller ASIC on a PCI Express minicard and driver software on the host computer. Vistas ReadyBoost and ReadyDrive components will support the Intel technology.
According to Grimsrud, while capacities of hard drives have improved, latency continues to be a performance bottleneck. As CPU performance has improved some 30 times over the past decade, hard disk latency has improved only 1.3 times in the same period.
"Its so grossly out of whack that for many workloads the disk drive ends up determining what the effective system performance is. As a CPU company, we obviously care about that," he said.
Accordingly, Robson was aimed at "bridging the gap" in performance between memory subsystems, he said.
However, unlike Microsoft, which left the management of the flash cache up to the memory vendors, Intel will take control of the flash hardware and software management for Robson.
Flash memory is susceptible to wear, and flash vendors employ algorithms to spread out erase cycles across all the cells on the flash memory as well as keeping a set of spares.
Grimsrud presented data on the endurance ratings of flash memory on the market. The Intel storage group has been concerned about the performance of flash for these applications, he said. The company found that a number of flash products on the market designed for consumer applications while rated for 100,000 cycles came up short and didnt offer the endurance necessary for enterprise applications.
"Weve also been surprised that the rate of endurance on the data sheet looks like its been made up by the marketing guys. Weve measured a lot of flash to failure and what we measured doesnt correspond to whats printed on the data sheet. The rated number of erase cycles ... missed by a mile. This was not an isolated case and not in thermal stress either," he said.
These comments were greeted by grumbling among the flash industry crowd. And Grimsrud admitted under questioning that the company hadnt tested all modules on the market, and that some products with "improved algorithms" were better.
Still, the wear levels reportedly werent up to Intels QA requirements for Robson and the company will use its home-grown NAND memory modules, Intel representatives said. Grimsrud said the company had developed a proprietary management driver technology that will be used in the Robson solution.
According to Grimsrud, one advantage of the Robson architecture over embedded flash management software was its tie to a powerful processor.
"With a Core Duo processor and the gigabytes of memory that are at our disposal, we can afford to do things that are intractable in a resource-constrained environment," he said.
Here are a few other views on Vistas use of flash, Robson and hybrid drives from the conference panels and exhibit hall:
So, Apple Computer, which now uses an Intel chip set, as well as Linux vendors could support Robson when the machines hit the market next year. Grimsrud was mum on the prospect.
"Theres no commitment yet for other operating system support based on what customers want," he said.
At Apples Worldwide Developers Conference, held in San Francisco concurrently with the Flash Memory Summit, Steve Jobs said the company was holding many features of Mac OS X Leopard, aka v10.5. Apple declined to comment on future Robson support.
Microsoft used an Ascender prototype drive in its demonstration. Ayers said the logo programs for ReadyBoost and ReadyDrive products will begin in June 2007.
Several new and novel advantages of flash-enabled drives were proposed at the conference. For example, Ayers suggested that some users reported that the drives were more quiet than conventional drives.
Don Barnetson, director of flash marketing for Samsung Semiconductor, of San Jose, said that if a flash subsystem can keep a hard drive powered down for 90 to 95 percent of the time, this can protect it during a fall.
"If your notebook is dropped, the odds will be that its going to be dropped when the hard drive isnt running. That can bring a 5X improvement in reliability for the drive," he said.
Barnetson said the companys first hybrid drives will ship with 256MB caches, which will support sleep times for drives of about 10 to 20 minutes.
"Over time we will grow the amount of cache in that hard drive. Rather than spin up a few times an hour, maybe we can get to the point where it spins only a few times a day," he said.
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