Huddled Masses
January 18th, 2007 | 
Author: Well, it looks like the days of Solid State Drives (SDD) are coming, and coming soon. Of course, if you’re a technology geek, you know that in some sense, they’ve already come. High end servers have been using flash-based drives with capacities of up to 100 GB for quite some time now, and they’re are much faster at reading data than regular Hard Disc Drives (HDD). However, this technology is just about ready to make it into the public eye and into the hands of your average Joe.
All of the major Flash retailers are now offering 32GB SSD drives, and with the arrival of Windows Vista, we have the first operating system which is natively aware of the needs of SSD cache management and able to take advantage of SSD capabilities to improve it’s performance. Since several of my friends have asked about flash discs after having read that they have short life spans, I figured it was worth writing down what I know about them.
The most important thing I can say about flash right now is that you should pay attention to the brand names. The most common flash chips have life-spans of only around 300,000 write cycles — you can read from them as much as you want, but if you write to the same block (that is, the same exact physical spot on the disc) it can fail after only 300,000 writes. However, my point is that not all flash is created equal, and the best flash chips can be rated as high as 1,000,000 write cycles per block.
On top of that, most flash drives nowadays use wear-leveling algorithms: since the wear is only on the write cycle, they swap data which is being written frequently with data that has exhibited a “read only” behavior … doing this can reportedly extend the life of the drive as much as 100 times the base life of the flash media.
This means that even if you read and write gigabytes of data every day, a flash-based SSD should last several years (experts claim the life expectancy of a conventional HDD can be as low as three to five years). On top of all of this, remember that with these bigger drives it is physically and financially feasible to add a DRAM cache into the drive which will not only make it faster, but can significantly improve it’s lifespan.
To give you an idea what we’re talking about here, the “Mean Time Between Failures” (MTBF) for hard disc drives had been going up fairly steadily from around 200,000 hours in the 1990’s to nearly 1,200,000 hours today (of course, we’re talking about top-of-the-line drives here). Just to be clear, when manufacturers measure the MTBF of a model, they do so only within what they call the “service life” of the drive. That is: if the MTBF of a drive is listed as 500,000 hours and the service life is five years, this means that a drive of that type is supposed to last for five years, and that of a large group of drives operating within this timeframe, on average they will accumulate 500,000 of total run time (amongst all the drives) before the first failure of any drive. So this doesn’t guarantee that your 500,000 hour drive is going to last 50 years. What it means is that if you replace the drive every five years, you would go (on average) almost 60 years before you had a drive failure.
Now, back to these these new SDDs that are coming out. All the major manufacturers seem to have 32GB models that are completely compatible with regular HDDs, so you can just take your your hard drive ans slide a flash drive in instead). They have input/output speeds as high as 62MB per second sustained, with random IOPS (input/output per second) at 7000 for a 512MB transfer (the fastest HDDs rate around 300-400 IOPS) and access times that are as much as 156 times faster (yeah, that’s not 156%, that’s 15,600%) ... all while using about 60% less power, and making no noise (both of which are really significant for laptops and media devices).
The bottom line is that a solid-state drive is going to be orders of magnitude faster than any hard disc drive, and the coup de grâce is that SanDisk is claiming a MTBF of 2,000,000 hours (the best I can find in hard disc drives is around 1,200,000). Of course, on the downside, their drive is going to cost you an extra $600 right now, but the point is everyone is getting into the market and competing, the prices are already coming down very quickly, and very soon you’re going to have an extra option when you start looking at drives for your next computer, laptop, or media center.
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Its just a shame that the drives cost so much.