Flash vs SSD

[YatBob]

The 2015 iMacs use flash storage , the 2017 iMac use SSD, what if any is the difference

 

[Darmok N Jalad]

The terms are somewhat interchangeable, as SSD = "Solid State Disk" (no moving parts) built from "flash" memory. The fastest drives now connect via PCIe lanes, while the first SSDs used the old SATA protocol. The 2015 iMac had already switched over to PCIe-based storage, so any performance difference between 2015 and 2017 will be from advancements in the SSD drives themselves.

 

[YatBob]

Thanks, kinda what I though although the terminology was confusing

 

[theluggage]

Thanks, kinda what I though although the terminology was confusing

Further to the other answer, SSD could refer to any type of "Solid State Disk" - whereas "flash" refers to a particular family of memory technology. Currently, the vast majority of SSDs use various flavours of flash memory, but these bad boys:

https://www.intel.com/content/www/u...aming-enthusiast-ssds/optane-900p-series.html

...are SSDs that use Intel's "Optane" (or "XPoint") technology which definitely isn't flash (and should be significantly faster than flash, especially when overwriting existing data).

Optane hasn't turned up in Macs yet, but may well do in the not-too-distant future.