Re: Is the checkpoint interval adjustable?

["Mike Audia" <mikey_a@gmx.com>]

> From: David Sterba
> There were a few requests to tune the interval. This finally made me to
> finish the patch and will send it in a second.

Thank you, David and to others who kindly replied to my post.  I will try your patch rather than modifying the code

> > >  Are there any unforeseen and effects of doing this?  Thank you for
> > > the consideration.
> >
> > I don't *think* that there should be. One way of looking at it is that
> > both 30 and 300 seconds are an *eternity* for cpu, memory, and storage.
> > Any trouble that you could get in to in 300 seconds some other machine
> > could trivially get in to in 30 with beefier hardware.
>
> That's a good point and lowers my worries a bit, though it would be
> interesting to see in what way a beefy machine blows with 300 seconds
> set.

I have my system booting to a BTRFS root partition.  Let's say I'm using a value of 300 for my checkpoint interval.  Does this mean that if I do a TON of filesystem writes (say I update my system which pulls down a bunch of system file updates for example), and I copy over several gigs of data from a backup, all _between_ checkpoints and for some reason, my system freezes forcing me to ungracefully restart... is EVERYTHING since the last checkpoint is lost?  Upon a reboot, will BTRFS just mount up to the last good checkpoiint automatically or will I have a broken system and need to add the `-o recovery` option while I mount it manualy from a chroot?

Another naive question: if I shutdown the system between checkpoints, systemd should umount my partitions.  Does the syncing of cached data occur after the graceful umount?