How does I/O for a RAID5 metadevice and a striped metadevice compare?
The striped metadevice performance is better than the RAID5 metadevice, but it doesn't provide data protection (redundancy).
RAID5 metadevice performance is lower than striped metadevice performance for write operations, because the RAID5 metadevice requires multiple I/O operations to calculate and store the parity.
For raw random I/O reads, the striped metadevice and the RAID5 metadevice are comparable. Both the striped metadevice and RAID5 metadevice split the data across multiple disks, and the RAID5 metadevice parity calculations aren't a factor in reads except after a slice failure.
For raw random I/O writes, the striped metadevice performs better, since the RAID5 metadevice requires multiple I/O operations to calculate and store the parity.
For raw sequential I/O operations, the striped metadevice performs best. The RAID5 metadevice performs lower than the striped metadevice for raw sequential writes, because of the multiple I/O operations required to calculate and store the parity for the RAID5 metadevice.