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Web-Server, File-Server, Workstation Patterns

The controllers are tested under loads typical of servers and workstations.

The names of the patterns are self-explanatory. The request queue is limited to 32 requests in the Workstation pattern. Of course, Web-Server and File-Server are nothing but general names. The former pattern emulates the load of any server that is working with read requests only whereas the latter pattern emulates a server that has to perform a certain percent of writes.

Thanks to efficiently selecting the more suitable disk in a mirror pair, the RAID10 arrays are considerably faster than the same-size RAID0 when there are only read requests to be performed. The degraded RAID10 is slower than its healthy counterpart but always ahead of the 4-disk RAID0 and, at low loads, even ahead of the 8-disk RAID0.

It is all simple and clear here: the more disks the array has, the higher its performance. And it does not really matter what type of array (RAID5 or RAID6) you use.

The degraded RAID5 and RAID6 both suffer a twofold performance hit due to the loss of one disk. The loss of a second disk in the RAID6 makes it almost as slow as the single HDD.

The performance ratings show that the RAID10 enjoy a large advantage over same-size arrays of other types at pure reading.

The standings change somewhat with the addition of write requests. The RAID10 are still in the lead under low loads but the RAID0 arrays go ahead at a queue depth of more than 32 requests.

There are significant changes in the second group of arrays, too. The 8-disk RAID6 falls behind the 8-disk RAID5 although the 4-disk arrays of these types are equals. The performance of the degraded RAID6 with one failed disk is much lower than that of the healthy array.

Thanks to good results at short queue depths the RAID10 are but slightly slower than the RAID0 in terms of performance ratings. The RAID5 and RAID6 arrays are slower than in the previous test.

The Workstation pattern has a large portion of writes and greatly different data block sizes. The RAID0 arrays are superior here. The RAID10 can only win at very short queue depths.

There are no changes among the checksum-based arrays. The standings are almost exactly like in the File-Server pattern.

The RAID10 are better according to our performance rating formula.

Take note that not only the degraded but also all of the healthy arrays, except for the 8-disk RAID5, are inferior to the single HDD at such load.

When the test zone is limited to 32GB, the arrays all accelerate and even the degraded RAID6 with two failed disks is ahead of the single HDD. The RAID0 arrays are now obviously better than the RAID10: the reduction of the test zone lowers the time to access data and reduces the effect of selecting the “luckier” disk in a mirror pair.

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