My daily readings 04/29/2013

    • Over the last decade CPU speeds have increased dramatically while disk access times have only improved slowly. This trend is likely to continue in the future and it will cause more and more applications to become disk-bound. […] Log-structured file systems are based on the assumption that files are cached in main memory and that increasing memory sizes will make the caches more and more effective at satisfying read requests. As a result, disk traffic will become dominated by writes.
    • Surprisingly, log-structured file systems are more relevant than ever when it comes to SSDs. The founding assumption of log-structured file systems – that reads are cheap and writes are expensive – is emphatically true for the bare-metal building blocks of SSDs, NAND-based flash. (For the rest of this article, “flash” refers to NAND-based flash and SSD refers to a NAND-based flash device with a wear-leveling, write-gathering flash translation layer.) When it comes to flash, reads may be done at small granularities – a few hundreds of bytes – but writes must be done in large contiguous blocks – on the order of tens of thousands or hundreds of thousands of bytes. A write to flash takes two steps: First the entire block is cleared, setting all the bits to the same value (usually 1, counter-intuitively). Second, individual bits in the block are flipped back to 0 until you get the block you wanted.
    • Don’t reserve for 3 years.

      AWS cuts their costs at a relatively reliable rate. We’ve done the match an found that the 1 year reservations are absolutely worth while, but that the 3 year reservations are not. Granted that was for our specific workload / use case.

      Money has a time value, and this stuff is getting cheaper fast.

  • tags: pm

Posted from Diigo. The rest of my favorite links are here.

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