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Subject: Re: sync vs async vs zfs
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>> 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?
>
> Correct. And I proved that on one of my servers in pre-prodcuction
> testing.

Tack-on question: would an identical-speed SLOG still speed up the pool 
by proxy simply by reducing IO load on the vdev(s) and/or reducing head 
travel on the drives?