Hi Richard, On 2015-06-20 21:40, Richard Weinberger wrote:
> Yesterday our git server faced a power cut and a git repository broke. > The server is running a ext4 filesystem on top of Linux 3.16 (stable > from openSUSE) and git 2.1.4. > We had a backup, so no data was lost but I really would like to figure out > what happened. > > This is the output of git fsck: > Checking object directories: 100% (256/256), done. > error: object file objects/ce/f7627fc160ad7294b1f728db0c1ddb65a38b1d is empty > error: object file objects/ce/f7627fc160ad7294b1f728db0c1ddb65a38b1d is empty > fatal: loose object cef7627fc160ad7294b1f728db0c1ddb65a38b1d (stored > in objects/ce/f7627fc160ad7294b1f728db0c1ddb65a38b1d) is corrupt > > To me it seems like git was creating a new object and got interrupted > before fsync/fdatasync'ing it. > As the object was referenced before syncing the data to disk the repo broke. > Could this have happened? > Also, is git designed to survive power cuts? Then referencing an > object before synching it do disk would make no sense. I had similar issues with ext4 in the past, even with local repositories when using Git without pushing. My then-current laptop would not report battery power correctly, so I ran into out-of-power situations that would result in a loose object file that was simply empty, i.e. its length was zero. As far as my analysis back then went, this was not Git's fault, because its `write_loose_object()` function would write to a temporary file first and only move that file into place once it was written fully. I was then shocked to learn that ext4 apparently has a default setting that allows it to truncate files upon power failure (something about a full journal vs a fast journal or some such) when I had expected the default to be a true journaled file system with proper atomicity regarding writes and moves. I remember that back then, I angrily fixed that setting to make my file system fully journaled. Maybe this leads you into the direction of a work-around in your setup? Ciao, Johannes -- To unsubscribe from this list: send the line "unsubscribe git" in
