Steve French wrote: > At the SMB3 test events over the last two weeks, we found out about a > new file attribute which Windows servers can return > "FILE_ATTRIBUTE_INTEGRITY_STREAM" (it can also be returned as an > fsinfo, volume, property - not just as a file attribute). > > The flag is set by the server in responses to query information about > a file when the underlying file system does checksumming of the data > and metadata for the file (similarly if the volume always checksums > data and metadata this flag would be enabled on the fsinfo response). > Apparently REFS when run in certain configurations (mirrored drives?) > or when formatted to require metadata/data integrity checksumming can > provide these extra guarantees. > > btrfs seems to support both metadata and data checksumming by default > and presumably if "check_int" is compiled in and enabled this is the > equivalent. What should Samba server use to check if data and > metadata integrity checksumming is enabled in btrfs? Are there any > other in-kernel filesystems that support metadata/data integrity > checksumming and how would Samba server detect them. > > SMB3 allows you (the app running on the client) to individually ask > the server's filesystem to enable or disable (metadata and data) > integrity checking on a directory or file - I don't know of any > equivalent on btrfs or any Linux file system. Is there an example of > a Linux file system that lets you set this on per file or directory > basis? > If I'm remembering correctly, btrfs does permit setting the 'nodatasum' option per-file, but doesn't expose that to userspace at this time. It *does* expose nodatacow (which implies nodatasum) via chattr +C (capital c), but that has some limitations. >From chattr man page: For btrfs, the 'C' flag should be set on new or empty files. If it is set on a file which already has data blocks, it is undefined when the blocks assigned to the file will be fully stable. If the 'C' flag is set on a directory, it will have no effect on the directory, but new files created in that directory will have the No_COW attribute. -- To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
