8 Matching Annotations
  1. Jun 2021
    1. the logical and physical page addresses are decoupled. A mapping table, which is stored on the SSD, translates logical (software) addresses to physical (flash) locations. This component is also called Flash Translation Layer (FTL).

      Flash Translation Layer (FTL)

    2. NAND flash pages cannot be overwritten. Page writes can only be performed sequentially within blocks that have been erased beforehand.

      Overwriting data on SSDs

    3. For example, if one looks at write latency, one may measure results as low as 10us – 10 times faster than a read. However, latency only appears so low because SSDs are caching writes on volatile RAM. The actual write latency of NAND flash is about 1ms – 10 times slower than a read.

      SSDs writes aren't as fast as they seem to be

    4. Another important difference between disks and SSDs is that disks have one disk head and perform well only for sequential accesses. SSDs, in contrast, consist of dozens or even hundreds of flash chips ("parallel units"), which can be accessed concurrently.

      2nd difference between SSDs and HDDs

    5. SSDs are often referred to as disks, but this is misleading as they store data on semiconductors instead of a mechanical disk.

      1st difference between SSDs and HDDs

  2. Feb 2021
    1. Jan 2021. I use a small, dedicated enterprise grade SSD as a swap drive. These enterprise drives can be bought for as little as $80 for 240GB right now, and are 3D nand with load leveling and other valuable improvements for swap. By using the drive only for swap, you pretty much guarantee it won’t affect your expensive terabyte level data drive should it fail, and you still get the performance of SSD. Estimates for very heavy use are about 2 1/2 years.
  3. Aug 2018
  4. Dec 2017