Re: WD Blue 510 SSD and strange write performance

Flash storage is complicated=2E I doubt there's a huge cache in them, as as=
 it would be volatile it'd be a big no-no for synchronous writes=2E The OS =
could cache it, of course=2E And if you're using ZFS then all bets are off=
=2E ZFS guarantees (for POSIX) that a synchronous write goes to non volatil=
e memory before the system call returns=2E However this does not mean it go=
es to the final location on the disk=2E ZFS has an intent log of stuff that=
 needs to be sorted out sometime, but is safe for now=2E So with can write =
away, especially with highly compressible blocks, and it'll go fast enough =
until it gets to the point it needs to get the FS in order (you run out of =
ZIL)=2E

I'm speculating about the cause of the effect in your case, but I'm not su=
rprised you're getting an effect=2E

Look up Flash storage strategies and the workings of the ZIL for more info=
rmation=2E