[OmniOS-discuss] re-tune round-robin reading from a mirror

[Schweiss, Chip]

This is a very interesting idea.  It could allow for the creation of a
scratch pool with great ROI.   I have a particular need for an extremely
high read rate pool for data analysis that will leverage the fattest read
optimized SSDs I can get for the dollar.  I was considering this to be
raidz1, but if mirroring with disks would work this way, it could be even
better bang for the buck.

Did you ever do any actual testing with this type of setup?  I'd love to
see some real world performance data.

-Chip

On Wed, Jul 15, 2015 at 10:09 AM, Jim Klimov <jimklimov at cos.ru> wrote:

> 15 июля 2015 г. 14:10:15 CEST, Michael Mounteney <gate03 at landcroft.co.uk>
> пишет:
> >Hello list;  is it possible with OmniOS to have a multi-way mirror with
> >one disk being an SSD and the rest magnetic;  then to tune ZFS to
> >perform all reads from the SSD?  for the sake of performance.  The
> >default case is round-robin reading, which is the best if all disks are
> >of approximately equal performance, especially if they're on separate
> >controllers.  But SSD changes that.
> >
> >______________
> >Michael Mounteney
> >_______________________________________________
> >OmniOS-discuss mailing list
> >OmniOS-discuss at lists.omniti.com
> >http://lists.omniti.com/mailman/listinfo/omnios-discuss
>
> When I last asked a few years ago (but IIRC forma mirror of local+iSCSI
> vdevs), the answer was along the lines that round-robin first considers the
> available devices. If the faster (ssd, local) device has no queue, it gets
> the load while the slower device still struggles with the task it has, so
> on average the faster device serves more io's - but not 100%. Queue depth
> tuning can also help here.
>
> Jim
>
> --
> Typos courtesy of K-9 Mail on my Samsung Android
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