[svlug] More links about ssds

Rick Moen rick at linuxmafia.com
Thu Jun 2 01:40:51 PDT 2016


Quoting Sarah Newman (newmans at sonic.net):

[links and information]

Thank you!

One of the subjects _not_ covered in my talk, though I certainly was
aware of it, was the subcategories of flash-memory architecture

SLC (single-level cell) gives best performance, but is most expensive
per GB.  SLC uses a single cell to store one bit of data.

MLC (multi-level cell) has become most common, is lower price per GB but
suffers higher wear rates and lower performance.  MLC can interpret four
digital states from a signal stored in a single cell. This makes it
denser for a given area and so cheaper to produce, but it wears out
faster.

eMLC (enterprise[1] MLC) is the same but surrounded by more amelioration
techniques than usual.

TLC (triple-level cell) stores three bits per cell for greater data
density and more capacious SSDs in the same form factor, but its
sustained write performance is comparatively quite poor, sometimes very
poor.



If we were all made of money, we'd ask for pure SLC NAND flash SSDs, but 
SLC SSDs are often a really exceptional balance of functionality for the
money.  (I would, however, try to avoid TLC flash in these devices.)


[1] As I commented in my talk, the word 'enterprise' in these contexts
means 'costs about 3x as much per unit'.




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