On Fri, May 15, 2020 at 11:27 AM Wols Lists <antli...@youngman.org.uk> wrote: > > The crucial point here is that dm-integrity protects against something > *outside* your stack trashing part of the disk. If something came along > and wrote randomly to /dev/sda, then when my filesystem tried to > retrieve a file, dm-integrity would cause sda to return a read error, > raid would say "oops", read it from sdb, and rewrite sda.
Yup. I understand what it does. Main reason to use it would be if it performs better than zfs which offers the same guarantees. That is why I was talking about whether lizardfs does overwrites in-place or not - that is where I'd expect zfs to potentially have performance issues. Most of the protections in lizardfs happen above the single-host level - I can smash a single host with a hammer while it is operating and it shouldn't cause more than a very slight delay and trigger a rebalance. That also helps protect against failure modes like HBA failures that could take out multiple disks at once (though to be fair you can balance your mirrors across HBAs if you have more than one). -- Rich
