Understanding SSD

SSD stands for Solid State Drive. Today, the “biggest bang for your buck” upgrade would be to upgrade your hard drive to SSD. Previously, used to be the memory. Any SSD you purchase today will have a performance boost of 10 to 15x compared to a conventional hard disk, except for size.

SSD are rated by performance (speed) and durability (material). 2 SSDs can be similar in size and performance, but prices may varies like heaven and earth. As with any flash drives (chip based storage), their quality (reliability) is measured by the type of chip they used to store data. Namely:

  • SLC = Single Level Cell flash (1 bit per cell)
  • MLC = Multi Level Cell flash (generally 2 bits per cell)
  • TLC = Triple Level Cell flash (3 bits per cell)

What does these terms mean and how would they affect your decision?

TLC chip would hold 3x more data compared to SLC making them higher data density per cell. This makes higher capacity SSDs cheaper to produce. Each flash cell have a lifespan and it deteriorates depending on the number of write cycles committed on that particular cell. If a cell dies, it will take with it the 3 bits of data that was stored in it. To lengthen an SSD lifespan, we recommend leaving at least 30% to 50% free space or buy an MLC or SLC NAND SSD (if your pocket is deep and filled with $$$).

So, if you were to filled your SSD to 98% full, that leaves only 2% free space. Since SSD is a random read / write, it is possible that the collective 2% free space maybe contributed by partially filled cells (scattered all over the SSD). This also means all temporary, swap and virtual memory files will be performed randomly on that 2% free space. This increases the write cycles of those affected cells and causing those cells to fail faster.

Leaving additional space (unallocated space) called “over-provisioning”. We would recommend leaving 10% of total SSD size “unallocated”. This will ensure your SSD performs at peak performances and extend your SSD lifespan.