Some Nerdy Stuff

April 8, 2010

Why are SSD’s so expensive?

Filed under: Uncategorized — aaronls @ 10:55 am

Basically a SSD is just a bunch of flash chips, with each chip providing a specific amount of storage space. Larger SSDs require more of these chips. These flash memory chips are built using 32nm and 45nm manufacturing processes on silicon, similar to CPUs. However, flash memory isn’t as complicated as a CPU and there are things like multi-level cell storage that flash uses to fit more data into a smaller space, so the cost isn’t quite as much as a CPU. Still, it takes several flash chips to provide the storage for an SSD. Additionally SSDs have additional components that add to the cost. For example chips that handle the flow of data to and from the flash memory. Some SSDs have extra flash storage that you don’t know about, because it is there on standby in case some of the flash memory goes bad and can replace the bad memory, so that as a user of the drive you don’t know something has gone wrong.  The process of making these chips is expensive.  Even if a single chip can hold 16 GB of data, it will take 4 of these to make a 64 GB SSD, and if you use the price of a really cheap CPU as a benchmark, then you are talking about $30 at least per chip.  So that’s $120 just for the flash memory on the drive and that doesn’t include the extra components that comprise the drive.

So it is a matter of the process of making flash memory is expensive. The other big factor is storage density. HDD manufacturers have managed to continually evolve hard drives such that they can fit more data in the same space, and thus similar manufacturing processes can produce more storage. For flash memory chips to get cheaper, manufacturers have to figure out how they can use the same/similar manufacturing processes but instead fit more storage space into the same flash memory chip. Increasing the storage density of the chip will make the cost per gigabyte of storage lower, since you are producing a chip with more storage using the same manufacturing process. So your manufacturing costs don’t go up significantly, but the amount of storage you’re producing does. The issue here is that increasing the storage density on silicon involves significant technology challenges to make the components of the chip smaller. The 45 nm and 32 nm processes currently used are named for the size of features on the chip, and making these features smaller so that more can be fit on the chip is a really difficult challenge.

Some recent research may improve storage density significantly in the next three years:
http://www.nytimes.com/2010/04/08/science/08chips.html?hpw

Another article explaining SSD cost in greater detail:
http://agigatech.com/blog/why-are-ssds-still-so-expensive/

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