Re: Unclear about CRUSH map and more than one "step emit" in rule

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On Sun, Nov 16, 2014 at 4:17 PM, Anthony Alba <ascanio.alba7@xxxxxxxxx> wrote:
> The step emit documentation states
>
> "Outputs the current value and empties the stack. Typically used at
> the end of a rule, but may also be used to pick from different trees
> in the same rule."
>
> What use case is there for more than one "step emit"? Where would you
> put it since
> a rule looks like
>
> rule <rulename> {
>
>         ruleset <ruleset>
>         type [ replicated | raid4 ]
>         min_size <min-size>
>         max_size <max-size>
>         step take <bucket-type>
>         step [choose|chooseleaf] [firstn|indep] <N> <bucket-type>
>         step emit
> }
>
> Hazard a guess: after "step emit" you start with step take... all over again?

Yep, that's it exactly. You could use this to do something like

step take ssd-root
step chooseleaf firstn 1 host
step emit
step take hdd-root
step chooseleaf firstn -1 host
step emit

-Greg
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