On Friday, 18 August 2017 2:52:20 PM AEST Stewart Smith wrote:
On 17 August 2017 1:22:09 pm AEST, Russell Coker via luv-main <luv- main@luv.asn.au> wrote:
XFS has no support for checksums that compares to ZFS and BTRFS. To do
XFS currently does metadata checksums.
There's work to get data checksums, but that's a larger on disk format change.
My understanding is that they just do checksums on blocks of metadata so if a block is corrupted that will be noticed. If a write to a block is missed and an old version of the block remains will that be noticed? If 2 blocks are written such that block 1 needed to be written first for correct behavior but block 2 remained committed after a power failure but block 1 wasn't will that be noticed? Writing a new copy of all the metadata up to the root of the filesystem as ZFS and BTRFS do) is the obvious way of solving this. But solving it by journaling everything and having checksums is a viable option too. BTRFS has support for "dup" metadata so if one copy is corrupt the other can be used. ZFS has a "copies=" option for filesystems to allow multiple copies of data. However many copies you have of data there will be one more copy of metadata in addition to whatever RAID options you might be using. A filesystem that has only a single copy of metadata will lose data if there is corruption. It's good to flag errors, but if you can't fix them the benefits are small. -- My Main Blog http://etbe.coker.com.au/ My Documents Blog http://doc.coker.com.au/