Re: How to debug intermittent increasing md/inflight but no disk activity?

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On Thu, Jul 11, 09:12, Dave Chinner wrote

> > Of course it’s not reproducible, but any insight how to debug this next time
> > is much welcomed.
> 
> Probably not a lot you can do short of reconfiguring your RAID6
> storage devices to handle small IOs better. However, in general,
> RAID6 /always sucks/ for small IOs, and the only way to fix this
> problem is to use high performance SSDs to give you a massive excess
> of write bandwidth to burn on write amplification....

FWIW, our approach to mitigate the write amplification suckage of large
HDD-backed raid6 arrays for small I/Os is to set up a bcache device
by combining such arrays with two small SSDs (configured as raid1).

Best
Andre
-- 
Max Planck Institute for Biology
Tel: (+49) 7071 601 829
Max-Planck-Ring 5, 72076 Tübingen, Germany
http://people.tuebingen.mpg.de/maan/




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