[ ... on the difference between number of devices and length of a chunk-stripe ... ]
> Note: possibilities get even more interesting with a 4-device > volume with 'raid1' profile chunks, and similar case involving > other profiles than 'raid1'. Consider for example a 4-device volume with 2 devices abruptly missing: if 2-length 'raid1' chunk-stripes have been uniformly laid across devices, then some chunk-stripes will be completely missing (where both chunks in the stripe were on the 2 missing devices), some will be 1-length, and some will be 2-length. What to do when devices are missing? One possibility is to simply require mount with the 'degraded' option, by default read-only, but allowing read-write, simply as a way to ensure the sysadm knows that some metada/data *may* not be redundant or *may* even be unavailable (if the chunk-stripe length is less than the minimum to reconstruct the data). Then attempts to read unavailable metadata or data would return an error like a checksum violation without redundancy, dynamically (when the application or 'balance' or 'scrub' attempt to read the unavailable data). -- 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
