But btrfs RAID-5 still suffers from the &#x27;write hole&#x27; problem where data can be permanently lost. We looked at RAID-5 performance for both ZFS and btrfs, and btrfs is about twice the throughput. One of the reasons for the performance difference is the following:
when ZFS writes a stripe, it waits for all blocks and the parity block to confirm they have been written before atomically updating the metadata for that stripe;
when btrfs writes a stripe, it just updates the metadata and  all blocks in parallel.
Hence if btrfs crashes, metadata may say a stripe is written but not all blocks are written.
It will be interesting to see the performance hit on btrfs when they finally fix the write hole problem. My prediction is that it will perform similarly to ZFS for RAID5.
Currently, for writes, we can get about 400MB&#x2F;s for btrfs RAID5, but only 220MB&#x2F;s for ZFS with five 5400 rpm 2.5&quot; disks.