[OmniOS-discuss] slog limits write speed more than it should

[Bob Friesenhahn]

On Fri, 14 Nov 2014, Rune Tipsmark wrote:

> 
> Looking at the first link he clearly states that ZIL is written to in a round robin fashion, I was under the
> impression that 2 log devices would then be faster than 1…unless mirrored of course.

This could be a mistaken impression.  The slog commits each write 
before proceeding to the next write.  If the involved SSDs have a 
fixed minimum write latency, then this would limit the maximum 
transaction rate regardless of the number of SSDs involved.  There 
could be an advantage to more SSDs if the additional time between 
writes allows the SSD to more effectively prepare for the next write 
and reduce the write latency.

Bob
-- 
Bob Friesenhahn
bfriesen at simple.dallas.tx.us, http://www.simplesystems.org/users/bfriesen/
GraphicsMagick Maintainer,    http://www.GraphicsMagick.org/