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IO prioritization: assume SRmax is the highest max (it usually will be). If not, find a compromise value for it so that | IO prioritization: assume SRmax is the highest max (it usually will be). If not, find a compromise value for it so that | ||
the other max numbers are within 4 threads of SRmax | the other max numbers are within 4 threads of SRmax. This is an old trick from Sun, set as follows; | ||
* SR: 4 - SRmax | |||
* SW: SRmax/2 - SRmax | |||
* AR 2 - ARmax | |||
* AW 2 - AWmax | |||
* Scrub 0 - 1 | |||
* VDEV max: SRmax * 1.25 | |||
These values are adjustable but are designed for SRmax, ARmax and AWmax to all be relatively high without fighting | |||
with each other. When SR or SW is saturated, they share SRmax worth of threads roughly equally, and allow AR and AW | |||
to share the remaining 20%. The low value for SRmin keeps sync reads from dominating other I/O. | |||
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