sync vs async vs zfs

Quartz quartz at
Thu Sep 24 20:53:27 UTC 2015

> Very short answer…

OK, thanks. So far that lines up with what I thought I knew. I still 
think I might be fuzzy on what constitutes an 'app' in this context 
though, presumably you're also counting services like nfs, etc? 
Basically, when considering just boring file copies, which things are or 
are not async and when? Under what circumstances is sync actually used 
in the real world?

>you can
> use a device which is much faster than the main zpool devices


1) A SLOG's only purpose is to reduce fragmentation and increase sync 
speed, correct? Re: speed, using a SLOG that's the same speed as the 
other drives in a pool is mostly pointless, right?

2) Async doesn't really care how your pool is constructed, and a SLOG is 
really the only thing that seriously makes a difference for sync, correct?

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