On Mon, Feb 06, 2017 at 09:36:58AM +0800, Qu Wenruo wrote: > > Please note the following things when calculating RAID5/6 data and P/Q > location: > > 1) Basic layout > The chunk stripe only shows the *first* full stripe layout. > And it always follows the sequence of "Data0, Data1, ... Data N, Parity" > > And one full stripe is consistent of N * 64K (fixed yet). > > > 2) Device rotation > RAID5/6 do device rotation. > So the *second* full stripe will have the following layout: > "Data 1, Data2, ... Data N, Parity, Data 0" > > > You can refer to my offline-scrub patchset to see how it assemble the > RAID5/6 mapping, which I believe it is easier than current btrfs_map_block() > implementation. > [PATCH v2 19/19] btrfs-progs: fsck: Introduce offline scrub function > > Thanks, > Qu Sorry for the delay in response, I was offline. Thanks for the details. I think now I have better idea about (1)Basic layout and (2)Device rotation. Will look into offline-scrub patches to explore more about exact mapping and on-disk layouts. I'm trying to understand layout for simple Raid-5 with 3-drives with 128KB file-size. Will try to understand Raid-6 little later. thanks.
Cheers. Lakshmipathi.G -- 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
