> I thought an important idea behind btrfs was that we avoid by design > in the first place the very long and vulnerable RAID rebuild scenarios > suffered for block-level RAID...
This may be true for SSD disks - for ordinary disks it's not entirely the case. For most RAID rebuilds, it still seems way faster with software RAID-1 where one drive is being read at its (almost) full speed, and the other is being written to at its (almost) full speed (assuming no other IO load). With btrfs RAID-1, the way balance is made after disk replace, it takes lots of disk head movements resulting in overall small speed to rebuild the RAID, especially with lots of snapshots and related fragmentation. And the balance is still not smart and is causing reads from one device, and writes to *both* devices (extra unnecessary write to the healthy device - while it should read from the healthy device and write to the replaced device only). Of course, other factors such as the amount of data or disk IO usage during rebuild apply. -- Tomasz Chmielewski http://wpkg.org -- 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
