Web-Server, Fileserver, Workstation Patterns
The controllers are tested under loads typical of servers and workstations. The server tests are the most interesting to us, being the most typical application for a RAID controller. Workstations may also have a high disk load, though.
The names of the patterns are self-explanatory. The Workstation pattern is used with the full capacity of the drive as well as with a 32GB partition. The request queue is limited to 32 requests in the Workstation pattern.
The results are presented as performance ratings. For the File-Server and Web-Server patterns the performance rating is the average speed of the drive under every load. For the Workstation pattern we use the following formula:
Rating (Workstation) = Total I/O (queue=1)/1 + Total I/O (queue=2)/2 + Total I/O (queue=4)/4 + Total I/O (queue=8)/8 + Total I/O (queue=16)/16.
Every array is faster than the single disk at request queue depths other than 1. The two-disk RAID1 behaves in a curious way: it is but slightly slower than the leaders at a queue depth of 2 but doesn’t speed up much as the queue gets longer. As a result, it shows lowest results at long request queue depths. The four-disk RAID10 is in the lead until a queue depth of 4 requests, being a little faster than the four-disk RAID0. The latter overtakes the RAID10 at longer queue depths, though. The RAID10 is always ahead of the three-disk RAID0.
The RAID5 arrays are not as fast as the RAID0 arrays with the same amount of disks but are overall good at this type of load. The RAID0 arrays boast good scalability of performance depending on the number of disks. The scalability of RAID5 is somewhat lower.
The performance ratings agree with the diagrams. The performance at short queue depths having a bigger weight, the RAID10 scores more points than the four-disk RAID0. Overall, the standings are the same as with the controllers we have tested before. Take note that the three-disk RAID5 and the two-disk RAID0 and RAID1 have very similar ratings.
The Web-Server pattern having no write requests, the mirrored arrays show their best thanks to their ability to alternate the requests between the disks of a mirror couple. As a result, the four-disk RAID10 wins the test at every request queue depth. The two-disk RAID1 is ahead of the two-disk RAID0. The RAID5 arrays are good at this load type, too. They deliver the same performance as RAID0 with the same amount of disks.
The Web-Server ratings agree with the diagrams and don’t need special comments.