On 2017-06-22 04:12, Qu Wenruo wrote: > > And in that case even device of data stripe 2 is missing, btrfs don't really > need to use parity to rebuild it, as btrfs knows there is no extent in that > stripe, and data csum matches for data stripe 1.
You are assuming that there is no data in disk2. This is likely, due to COW nature of BTRFS. But it is not always true. Anyway, the same problem happens if you are writing data on disk2 . If a) data (disk2) is written b) parity is not updated (due to a power failure) until that you don't lose anything, but if c) disk1 disappear you are not in position to recompute valid data in disk1 using only data2 and parity > No need to use parity at all. > > So that's why I think the hole write is not an urgent case to handle right > now. > > Thanks, > Qu -- gpg @keyserver.linux.it: Goffredo Baroncelli <kreijackATinwind.it> Key fingerprint BBF5 1610 0B64 DAC6 5F7D 17B2 0EDA 9B37 8B82 E0B5 -- 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
