On Tue, Mar 26, 2024 at 3:34 AM Pankaj Raghav <kernel@pankajraghav.com> wrote:
> One question: Does ZFS do something like FUA request to force the device
> to clear the cache before it can update the node to point to the new page?
>
> If it doesn't do it, there is no guarantee from device to update the data
> atomically unless it has bigger atomic guarantees?
It flushes the whole disk write cache (unless you turn that off).
AFAIK it can't use use FUA instead yet (it knows some things about it,
there are mentions under the Linux-specific parts of the tree but that
may be more to do with understanding and implementing it when
exporting a virtual block device, or something like that (?), but I
don't believe it knows how to use it for its own underlying log or
ordering). FUA would clearly be better, no waiting for random extra
data to be flushed.