Seagate Launches Hybrid SSD Hard Drive

MojoKid writes "Though there has been some noise in recent years about hybrid storage, it really hasn't made a significant impact on in the market. Seagate is taking another stab at the technology and launched the Momentus XT 2.5-inch hard drive that mates 4GB of flash storage with traditional spinning media in an attempt to bridge the gap between hard drives and SSDs. Seagate claims the Momentus XT can offer the same kind of enhanced user experience as an SSD, but with the capacity and cost of a traditional hard drive. That's a pretty tall order, but the numbers look promising, at least compared to current traditional notebook hard drives."

Re:4GB?

[WrongSizeGlass]

The cache is 4GB, the drive is up to a 500 GB 'traditional' drive.

Try adjusting the swapPINESS

[tepples]

What swapfile? I have used Ubuntu on a few PCs with at least half a GB of RAM, and I rarely see swap usage climb above 40 MB. In an environment where reads are cheaper than writes, you'll want to use a low value for the swappiness [ubuntu.com], such as 10% instead of the default 60%.

Re:Gets Better Over Time

[eln]

These days with RAM being so cheap, your swap space is basically a warning that things are going terribly wrong. You want your swap on slow storage because slow storage is cheap and your swap should see very few writes under normal operation. If your machine starts hitting swap like crazy, you'll know immediately because your performance will go straight down the crapper as it feverishly tries to write to slow storage. This is your cue to figure out what's wrong and fix it ASAP so your machine will stop thrashing.

SLC flash

[Animal Farm Pig]

According to the article, it's SLC flash. It should have many more write-erase cycles than MLC.

Re:So they make a hard drive with a cache?

[dingen]

The difference between this drive and every other drive on the markt is not the fact it has a cache. Every harddisk has a cache. The difference is: this drive has a 4 GB cache. And because it's an SSD cache and not (as you suggest) a RAM cache, it maintains it's state even between reboots, so your computer is fast right from the start.

Re:Hmmm...

[dingen]

No, because then every time your computer reboots, you need to fill the cache again. Using a solid state cache, you need to fill the cache only once and then keep it updated according to your usage, but a reboot wont harm performance at all.

Re:ReadyBoost in hw?

[Sockatume]

Microsoft actually did pitch "ReadyDrive" [wikipedia.org] hybrid SSDs as a selling point for Vista back when it launched. It was basically the same as this, except the caching was controlled in the OS and not the drive and it did some fancier stuff like caching boot data on shutdown. It didn't do very well, perhaps because the technology wasn't mature enough in price and speed.

Re:A glaring omission by Seagate

[DaveV1.0]

They haven't been omitted. You need to read the second link. IOPs and read/write speeds are about 1/3 and 2/3 of the way down the page, respectively.

Re:4GB?

[InfiniteWisdom]

Yes [storagesearch.com]

Re:Or wait..

[Arthur Grumbine]

Should it be "much" instead? I'm not a native English speaker, so if you could enlighten me on how to use the language correctly, I would be thankful.

"Much" would be correct. In general, "much" is used when speaking without reference to any kind of unit (e.g. oil, power, land, money, data, etc), while "many" is used when speaking with units (e.g. barrels, kilowatts, hectares, dollars, bytes).

Re:4GB?

[Bigjeff5]

Yeah, that wikipedia article is using figures from over a decade ago (1997 for their highest NAND numbers). Today the number of write cycles for the premium chips are in the millions, not thousands. You'd have to write your entire 500gb hard drive 8,000 times to burn up that 4gb of flash, assuming 1 million write cycles. In these applications, though, they're probably using the "creme de la creme" of flash chips, which can last up to 5 million write cycles. That lets you write that 500gb hard drive 45,000 times before the flash dies. That's 22.5 petabytes worth of data transfer. Assuming an 11ms write time for the hard drive (typical of notebooks), and assuming I didn't royally screw up somewhere (I may have), I get 32 million years of non-stop writing to use that up.

Even at their slowest, SSD drives are 5-10x faster than spinning disks. This allows it to act as a perfect layer of cache between RAM and HDD. It's also non-volatile, like the rest of the hard drive, so all you need to ensure no loss of data is to at least get the data to the cache. Assuming the hard drive doesn't do something retarded, like wipe the cache on reboot, it's all good.

Re:Gets Better Over Time

[TheRaven64]

Easily? I think not.

Swap tends to be demand paging, where you're loading in a page as it's accessed (and writing a page out to make room, although this happens asynchronously with a little buffer). Satisfying page faults from a drive with a 5ms access time limits you to around an 800KB sustained transfer rate for reading. If you're lucky, you can do sequential writes so you keep your 800KB/s write rate. At this rate, you'd only use 7GB/day on swapping, if all of your disk I/O is swapping and you are swapping constantly for 24 hours. If you're writing more than a few hundred MBs per day to swap then you are going to notice that your machine has really terrible performance.