Btrfs RAID: Built-In/Native RAID vs. Mdadm

When conducting random reads with the Flexible I/O Tester, the mdadm-based Btrfs RAID was noticeably faster at all levels except for RAID 1.

In carrying out random writes, the built-in RAID support to the Btrfs file-system on the Linux 3.18 kernel was noticeably faster than the mdadm-configured software RAID.

FIO showed the mdadm-based configuration doing better than the native Btrfs RAID for the RAID 1 and 10 levels with sequential reads. RAID 0 failed with mdadm Btrfs for the sequential reads.