On Thu, 20 Aug 2015 11:55:43 AM Chris Murphy wrote: > > Question 1: If I apply the NOCOW attribute to a file or directory, how > > does that affect my ability to run btrfs scrub? > > nodatacow includes nodatasum and no compression. So it means these > files are presently immune from scrub check and repair so long as it's > based on checksums. I don't know if raid56 scrub compares to parity > and recomputes parity (assumes data is correct), absent checksums, > which would be similar to how md raid 56 does it. Linux Software RAID could recreate a mismatched block from RAID-6 parity but doesn't do so. It could be that a block was changed correctly but didn't get the parity data written so such "correction" would be reverting a change. So Linux Software RAID only regenerates parity for a scrub and makes both disks have the same data for RAID-1. There's no good solution to these problems without doing the sorts of things that WAFL, ZFS, and BTRFS do. -- 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 majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
