RAID5 Metadevices and Striped Metadevices

This section compares performance issues for RAID5 metadevices and striped metadevices.

• 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.