06-01-11: Bob_reynolds
What's the fundamental difference between compact flash, USB flash, SD cards, and solid state drives?
Hi Bob,
While there are a number of fundamental differences between flash memory technologies that have been and are being used (NAND/NOR, SLC/MLC, manufacturing "process" (i.e., the number of nanometers of the smallest feature size), speeds, capacities, etc.), I don't think that there is any specific relation that can be defined between those technological differences and the different formats you listed. It's basically a matter of the different formats having been introduced at different times by different manufacturers, and having achieved differing degrees of market penetration into different applications.
I've not kept up, but what's the average number of writes SSD devices are capable of these days?
100,000 in some cases, 1,000,000 in others. I'm not sure, though, if those figures are for the number of erase/write cycles of an individual block, or for the total number of cycles applied to all blocks.
Differences in approaches to wear leveling, bad block management, and error correction, though, will mean that the same memory chip, rated for a given number of cycles, won't necessarily provide the same or even similar longevity in different devices.
When SSD's were initially introduced, I was skeptical about their ability to withstand the number of erase/write cycles that would occur over time in an operating system drive application, but to this point I haven't seen any indications that it has turned out to be a significant problem. And SSD's are now commonly offered with three year warranties. I'm using one as the os drive in a computer I built about 9 months ago, and I couldn't be happier with it.
For local secondary storage, do we really need the performance benefit of solid state?
Along the lines of my earlier post, SSD's appear in the near term to be cost prohibitive for mass storage applications. When and if that changes, the only advantage I can see is the possibility of greater reliability, and less chance of data loss if data is not backed up as it should be, since there are no mechanical parts to wear out, and in that kind of application SSD's erase/write cycle limitations would presumably be much less relevant than for an os drive.
Best regards,
-- Al
