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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.
The Web-Server pattern consists of read requests only. The RAID10 are somewhat faster than the RAID0 thanks to reading from the faster disk in the mirror even though this technique is not very efficient here (we have seen better results in our previous test sessions). The degraded RAID10 slows down heavily at long queue depths, being just a little faster than the 4-disk arrays. At short queue depths (up to 8 requests) it is about as fast as the healthy array.
The RAID5 and RAID6 arrays are equals here if they have the same amount of disks. The degraded arrays have a difficult time, though. The degraded 8-disk RAID5 is only as fast as the 4-disk RAID5. The RAID6 slows down even more than one of its disks fails. When two disks fail, the RAID6 is just hardly faster than the single HDD.
The performance ratings show that the array type has little importance under such load while the amount of disks in the array is the decisive factor.
When there are write requests in the load, the RAID10 are slower than the RAID0 at long queue depths although the arrays are close at short queue depths. The performance of the RAID0 is growing up at a faster rate as the queue is increasing.
The RAID6 arrays fall behind the RAID5 ones in the File-Server test. Take note of the behavior of the degraded 8-disk arrays: the performance of the degraded RAID5 is higher than that of the 4-disk RAID5 while the degraded RAID6 (without one disk) is slower than the 4-disk RAID6. When working with two failed disks the RAID6 is ahead of the single HDD at short queue depths but sinks to last place at long queue depths.
The number of disks is still the decisive factor, but the type of the array becomes important, too, if your server is going to process some write requests. The checksum-based arrays have lower performance but offer the higher fault tolerance of RAID6 and higher capacity than in RAID10.
