I had a 4 drive RAID10 btrfs setup that I added a fifth drive to with the "btrfs device add" command. Once the device was added, I used the balance command to distribute the data through the drives. This resulted in an infinite run of the btrfs tool with data moving back and forth across the drives over and over again. When using the "btrfs filesystem show" command, I could see the same pattern repeated in the byte counts on each of the drives.
It would probably add more complexity to the code, but adding a check for loops like this may be handy. While a 5-drive RAID10 array is a weird configuration (I'm waiting for a case with 6 bays), it _should_ be possible with filesystems like BTRFS. In my head, the distribution of data would be uneven across drives, but the duplicate and stripe count should be even at the end. I'd imagine it to look something like this: D1: A1 B1 C1 D1 D2: A1 B1 C1 E1 D3: A2 B2 D1 E1 D4: A2 C2 D2 E2 D5: B2 C2 D2 E2 This is obviously over simplified, but the general idea is the same. I haven't looked into the way the "RAID"ing of objects works in BTRFS yet, but because it's a filesystem and not a block-based system it should be smart enough to care only about the duplication and striping of data, and not the actual block-level or extent-level balancing. Thoughts? Thanks in advance! Tom -- 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
