On Thu, 20 Aug 2015 10:09:26 PM Austin S Hemmelgarn wrote: > > 2: Out of curiosity, why is data checksumming tied to COW? > > There's no safe way to sanely handle checksumming without COW, because > there is no way (at least on current hardware) to ensure that the data > block and the checksums both get written at the exact same time, and > that one of the writes aborting will cause the other too do so as well. > In-place compression is disabled for nodatasum files for essentially > the same reason (although compression can cause much worse data loss > than a failed checksum).
A journaling filesystem could have checksums on data blocks. If Ext4 was modified to have checksums it would do that. But given that a major feature of BTRFS is snapshots it doesn't make much sense to implement a separate way of managing checksums. I think that ZIL is the correct way of solving these problems. -- My Main Blog http://etbe.coker.com.au/ My Documents Blog http://doc.coker.com.au/ -- To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html
