Geom Raid5 - Comparing To Other Software RAID5 Solutions

Comparing To Other Software RAID5 Solutions

geom_raid5 distinguishes itself by providing both advanced features and high performance. While the theoretical maximum write speed is · ( - 1), the latest version is able to achieve about 80% of that theoretical maximum. This is in huge contrast with other software RAID5 solutions which sometimes achieve less than 10% of that throughput combined with significantly higher CPU utilization.

The reason for this huge difference lies in geom_raid5's design. In order to write data to a RAID5 volume, data must often first be read in order to calculate the parity information that protects against data loss in case of a single disk failure. Using request combining a full stripe block can be 'collected' so a read is no longer required. This means the harddrive heads do not need to change position every time but can write data contiguously, theoretically at full speed.

Of course, this only works with sequential transfers and sometimes even then the filesystem does not write contiguously. But using request combining, geom_raid5 manages to outperform any software RAID5 solution to date, capable of reaching write-speeds associated with hardware RAID5 on budget-level x86 hardware.

Currently the module is being finalized. When a stable version is released the author will release further information about its design and disclose benchmarks. In particular, benchmarks showing geom_raid5 performance versus ZFS's RAID-Z are long awaited by users.