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Re: WAPBL/cache flush and mfi(4) (Manuel Bouyer) writes:

>How do you think this should be handled ? have a sysctl to control
>mfi's behavior per-controller (eventually with default depending on BBU
>status), or have a vfs.wapbl.flush_disk_cache per mount-point
>(with a mount option maybe) ? 

WAPBL really needs the cache flush operations, so while disabling it
for debugging is probably useful, I don't think that we need to
offer finer controls.

You can ignore the flush operation when the controller has a working BBU
except for shutdown/suspend.

For controllers without BBU, there should be a limit on how much write data
it is allowed to keep dirty in the cache, so that a flush can finish
quickly. The standard drivers always turn off write caching when the BBU
is not working.

                                Michael van Elst
                                "A potential Snark may lurk in every tree."

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