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Optimizing Linux with cheap flash drives
Posted Feb 19, 2011 10:40 UTC (Sat) by arnd (subscriber, #8866)
High-end SSDs come with significant amounts of RAM that can be used to hide most of the nasty effects, or to do something much smarter altogether, such as implementing the entire drive as a log structured file.
The caching unfortunately makes it a lot harder to reverse-engineer the drive through timing attacks, so it's much harder to tell what it really does.
What we know is that the underlying NAND flash technology is very similar, so in the best case, an SSD will be able to hide the problems, but not completely avoid them. If I were to design an SSD controller, I'd do the same things that I'm suggesting in https://wiki.linaro.org/WorkingGroups/KernelConsolidation...
Posted Feb 19, 2011 18:23 UTC (Sat) by aleXXX (subscriber, #2742)
Actually I can remember that when writing to raw NAND we had also rates somewhere in the 10 to 15 MB/s range.
Posted Feb 19, 2011 20:03 UTC (Sat) by arnd (subscriber, #8866)
* SATA is a much faster interface than SD/MMC
* NCQ and write caching allows optimizing the accesses by reordering and batching NAND flash accesses
* Using SLC NAND instead of MLC improves raw accesses
* Using multiple NAND chips in parallel gives a better combined throughput
* Expensive microcontrollers on the drive can use smarter algorithms
All of these cost money, so you don't find them on the low end drives that I analyzed.
Posted Feb 20, 2011 9:12 UTC (Sun) by alonz (subscriber, #815)
Posted Apr 6, 2011 18:36 UTC (Wed) by taggart (subscriber, #13801)
Posted Apr 20, 2011 19:12 UTC (Wed) by dmarti (subscriber, #11625)
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