Andy Ruhl <acr...@gmail.com> writes: > If solving your problem depends on sync frequency, I don't see why > this shouldn't be managed by some knob to twiddle. Given that the > crash scenario doesn't get worse depending on where the knob is or if > the crash happens while the knob is working. If it does, it's > pointless.
My sense is that Donald isn't complaining about why is the sync frequency 30s instead of 60s; it's more bafflement at waiting 10-15 minutes with an idle disk and having the data not synced at all. There's a historical period of 30s, and that seems both not often enough not to cause trouble and often enough to not boggle users. It may also make sense to have a syncer behavior that is low rate, to not overwhelm asked-for IO, and to use most of the disk bandwidth when it is on, and to let it be otherwise, for laptops. But a basic correctness property is almost certainly that if the disk is spun up and is not in heavy use and lots of time passes, dirty buffers (data and metadata) are written to disk.
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