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Seagate Releases Hybrid Hard Drive
An anonymous reader writes to tell us Seagate has released a new hybrid hard drive. This new drive adds the speed of a solid state drive to the conventional hard drive. Originally designed for laptops this new drive comes in 80, 120, and 160 GB flavors and features 256MB of flash memory.
I'm assuming (TFA is slashdotted) because the flash is used as kind of persistent cache. If so you could confidently defer a write onto the actual platter until you are doing other things in the neighborhood, confident that the data will be there if something goes wrong like a power failure or crash. I don't think it would do much for read caching, for which volatile RAM is fine.
Statistically, 256MB of pending sectors is probably enough to get most of the potential benefits from reorganizing writes to the platter. And if you sell a gazillion of these, a buck saved on each unit is a gazillion dollars of profit.
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This is about having longer laptop battery life. These days, processors are pretty good at throttling back. So the next big consumers are the harddrive and the screen (or rather its backlight). Well, hybrid harddrives offer a potential solution. Cache frequently needed data and small writes to flash, and you can spin up the drive platters less often. That saves power which increases the time you get on battery. Also it actually will make a laptop MORE responsive in that if the disk is spun down, the flash can handle things as it spins up so everything doesn't have to come to a halt waiting for it.
I don't know how much of a use these will be in desktops, but in laptops it seems like a really good idea. Also, Seagate drives normally perform slower than the competition. In basically all the tests I've seen, their drives are on the bottom. Of course we are talking a difference of a few percent at most, and perhaps that's also the reason their drives last longer. Maybe they don't push them so hard.
They tested two 5400RPM hybrid drives against a 7200RPM standard drive... the results are as expected. Now I do agree that if I'm going to shell out the extra cash for the hybrid I probably want the 7200 drive too... and I definitely agree that I'd wait a couple generations (dunno about years)
Why does any of this require OS hooks? If you're going to have OS hooks, you might as well glue a USB thumb drive to the hard drive and be done with it. (And in fact, an md-like linux driver to combine two block devices in a manner like the above would be a great hack.)
The real world benefits of using flash as a cache layer between the harddrive and the computer, either through hybrid drives, don't seem to have materialized yet.
With my thinkpad there was an optional gig of flash that I ordered. After I downloaded the drivers and got it all set up, I found that there wasn't any noticiable difference in speed, or harddrive usage. However, I did notice that it interacted poorly with the "active protection" feature that stops the harddrive whenever the computer is in motion. Whenever the computer was unplugged, the flash cache was turned on, I could simply shake my computer (thus activating active protection) to get a blue screen.
Furthermore a little research showed that benchmarks on flash caches being sold right now offered no performance benefit whatsoever.
If there's no performance benefit, why are they trying to sell these things to people? I've seen some handwaving over the idea that flash *might* keep the harddrive from spinning most of the time and thus save battery life. However, when using the flash I saw no noticeable benefit.
Having an extra layer of cache in the system architecture seems like a good idea on paper, but in the real world the consumer is buying totally worthless pieces of hardware that do not improve performance one whit, and have never been proven to improve battery use.