On Thu, May 12, 2016 at 07:34:26AM +0800, ching wrote: > for example https://btrfs.wiki.kernel.org/index.php/Manpage/btrfs-scrub btrfs scrub is designed to make sure all the blocks and checksums are consistent. Ching makes a good point that it would be helpful to have a way to access the underlying backing device directly to ensure it is consistent. I think currently you can use dmsetup with an offset to get the real filesystem past the bcache header, mount that read only somewhere and scrub that. Not ideal because scrub will not be able to fix issues that are fixable, but at least it should report errors. Would that work? Marc > On May 12, 2016 3:13:22 AM GMT+08:00, Eric Wheeler <bcache@xxxxxxxxxxxxxxxxxx> wrote: > >On Wed, 11 May 2016, ching lu wrote: > > > >> The read cache prevent the program to scrub the backing device > >directly. > >> > >> if a few bits flipped in the backing device, the cache may still > >> return healthy data for a while. > >> > >> Must i remove cache device before scrubbing? > > > >What do you mean by scrub? > > > >-- > >Eric Wheeler > > > >> > >> > >> On Wed, May 11, 2016 at 9:15 AM, Eric Wheeler > ><bcache@xxxxxxxxxxxxxxxxxx> wrote: > >> > On Fri, 29 Apr 2016, ching lu wrote: > >> > > >> >> Hello, > >> >> > >> >> i want to develop a script to perform data scrubbing periodically. > >> > > >> > I think you want to set dirty_percent to 0 and > >cache_mode=writethrough. > >> > Then wait a long time for dirty_percent to actually reach 0. > >> > > >> > -- > >> > Eric Wheeler > >> > > >> > > >> >> > >> >> For my use case, i think it is meaningless to scrub cached data. > >> >> > >> >> If i change the cache mode to "none", will it turn off the read > >cache too? > >> >> > >> >> Furthermore, will this invalidate cached data? (i do not want to > >"warm > >> >> up" the cache again after the scrubbing) > >> >> > >> >> Thanks in advance, > >> >> c > >> >> -- > >> >> To unsubscribe from this list: send the line "unsubscribe > >linux-bcache" in > >> >> the body of a message to majordomo@xxxxxxxxxxxxxxx > >> >> More majordomo info at http://vger.kernel.org/majordomo-info.html > >> >> > >> -- > >> To unsubscribe from this list: send the line "unsubscribe > >linux-bcache" in > >> the body of a message to majordomo@xxxxxxxxxxxxxxx > >> More majordomo info at http://vger.kernel.org/majordomo-info.html > >> > > -- > To unsubscribe from this list: send the line "unsubscribe linux-bcache" in > the body of a message to majordomo@xxxxxxxxxxxxxxx > More majordomo info at http://vger.kernel.org/majordomo-info.html > -- "A mouse is a device used to point at the xterm you want to type in" - A.S.R. Microsoft is to operating systems .... .... what McDonalds is to gourmet cooking Home page: http://marc.merlins.org/ | PGP 1024R/763BE901 -- To unsubscribe from this list: send the line "unsubscribe linux-bcache" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
