Hi, In order to close the RAID5 write hole, I prepose the add a mount option that would change RAID5 (and RAID6) behaviour : . When overwriting a RAID5 stripe, first convert it to RAID1 (convert it to RAID1C3 if it was RAID6) . Have a background process that converts RAID1 stripes to RAID5 (RAID1C3 to RAID6) Expected advantages are : . the low level features set basically remains the same . the filesystem format remains the same . old kernels and btrs-progs would not be disturbed The end result would be a mixed filesystem where active parts are RAID1 and archives one are RAID5. Regards, Hubert Tonneau
