sync vs async vs zfs

Quartz quartz at
Fri Sep 25 02:05:39 UTC 2015

> I expect that system utilities like cp and tar do not do sync writes.
> sync writes are supposed to be a special case, used only when needed.
> I run into them with VBox writing to<>.vmdk files.

NFS forces sync though, doesn't it? What if you're cp-ing to a mounted 
share? I'm not sure I totally understand how all this interacts.

>> 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?
> Not quite true. Once you get through the ARC the configuration of the
> zpool _will_ matter to performance.

Maybe I worded that badly. What I meant was that whereas sync write 
performance is strongly affected by a SLOG, async writes have no special 
considerations of their own that don't also affect sync, right?

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