On 8/26/2011 1:01 AM, Gregory Maxwell wrote: > On Wed, Aug 24, 2011 at 9:11 AM, Berend Dekens <bt...@cyberwizzard.nl> wrote: > [snip] >> I thought the idea of COW was that whatever happens, you can always mount in >> a semi-consistent state? > [snip] > > > It seems to me that if someone created a block device which recorded > all write operations a rather excellent test could be constructed > where a btrfs filesystem is recorded under load and then every partial > replay is mounted and checked for corruption/data loss. > > This would result in high confidence that no power loss event could > destroy data given the offered load assuming well behaved > (non-reordering hardware). If it recorded barrier operations the a > tool could also try many (but probably not all) permissible > reorderings at every truncation offset. > > It seems to me that the existence of this kind of testing is something > that should be expected of a modern filesystem before it sees > widescale production use.
Gregory, Thank you for the idea to implement a tool that verifies the file system consistency. Following your idea, I have just written a runtime tool for this purpose, refer to the message-id <cover.1320849129.git.sbehr...@giantdisaster.de> in the btrfs mailing list. The tool examines all btrfs disk write operations at runtime. It verifies that the on-disk data is always in a consistent state, in order to create confidence that power loss (or kernel panics) cannot cause corrupted file systems. -- To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
