Who thought that the kind of memory built into tiny USB flash drives could be used at giant data centers to reduce power consumption by as much as 90 percent?
Researchers from Princeton’s School of Engineering and Applied Science have written a program called SSDAlloc. In principle it’s simple: it tells a computer running on RAM (random access memory) to pretend that it’s running on flash memory.
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Here’s why. RAM, which is used on most computers, stores information on the hard drive as a charge. Turn the power off and the charge disappears and with it, your data. This is why a computer can lose a document if you don’t save it to the hard drive.
Flash is different. It stores information in electrons even without any power input.
Flash has made inroads as an option for hard drives, and it’s a lot faster, since there are no moving parts. (A hard drive has to spin up and spin down, which takes time). Even so, most computers don’t take advantage of the speed because of the way a computer’s operating system searches for data. Most computers are designed to look in the RAM first for the data it needs. Only after that does the operating look elsewhere, such as on a the hard drive or a flash drive. That kind of hierarchical searching around can really slow things down, because it creates a bottleneck.
So Vivek Pai, an associate professor of computer science and graduate student Anirudh Badam thought they could take advantage of the speed of flash and eliminate the bottleneck. Badam wrote software that lets programmers bypass the traditional system of searching for information in RAM memory first. The SSDAlloc program moves the flash memory up in the internal hierarchy of computer data. The flash drive, for instance, gets to be first in line rather than last. That makes flash drives a much better option for big data centers.
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By allocating memory this way, a computer can offload a lot of the work to flash memory and avoid the heavy power use of either RAM or hard drives. Cutting down on the power used also reduces the amount of heat the computers generate. Data centers have to spend a lot of money — and energy — in cooling. Some major Internet companies, like Facebook, are moving their data centers to Arctic latitudes to keep them cool. Gamers deal with this too, and water-cooled machines are popular with power users who need massive amounts of computing oomph for running the latest version of Grand Theft Auto or Final Fantasy.
A version of SSDAlloc is being used by one flash memory manufacturer, Fusion-io, of Salt Lake City.
Why didn’t anyone think of this before? For one thing, flash drives are a relative newcomer. The first solid-state drives didn’t hit the mass market laptops until 2007 with the Asus Eee PC subnotebook. The small flash drives that most people know didn’t become ubiquitous until relatively recently, and before that, the cost of flash memory was high enough that most computers didn’t use it for storage. Flash is still a bit pricey — a MacBook Air is much more expensive per megabyte of storage than its cousins with traditional hard drives. Data centers can’t afford to switch en masse to flash; not without a more compelling reason. SSDAlloc may provide one.
Another factor is the speed and power of more recent machines. Computing speeds have gone up quickly in the last few years, and with that, the heat exchange issue has become more acute. And though data centers might have used flash memory before to save power, the energy use wasn’t as big of a concern until recently.
via Princeton University
Photo: A google Data Center in The Dalles, Oregon. Google currently uses enough power in its data centers to power thousands of homes. Credit: Wikimedia Commons