The linear read speeds are equal for both file systems, so we draw a common diagram:
It seems like the three- and four-disk RAID0s should exchange their places. However, these results are true. At linear reading, the speed depends linearly on the number of disks, i.e. two-, three- and four-disk RAID0 arrays should provide a double, triple and quadruple speed of the single drive. We don’t see it here. Moreover, we see the four-disk RAID0 performing slower at the beginning of the disk than the three-disk RAID1! The dependence of the performance of RAID5 on the number of disks is obvious, although it is not proportional to the number of disks in the array. The linear speed of reading from RAID1 array is close to the speed of the single drive while RAID10 loses to the two-disk RAID0.
The linear read speed doesn’t depend on lazy write actually, and this was true for most modes. Curiously, the speed of reading the beginning of RAID0 array is higher when the disk caching is disabled.
These are the read graphs for each of the arrays:
- Linear read graph for JBOD (1 HDD);
- Linear read graph for RAID0 (2 HDDs);
- Linear read graph for RAID1 (2 HDDs);
- Linear read graph for RAID0 (3 HDDs);
- Linear read graph for RAID5 (3 HDDs);
- Linear read graph for RAID0 (4 HDDs);
- Linear read graph for RAID5 (4 HDDs);
- Linear read graph for RAID10 (4 HDDs).
For checking out the controller’s ability to keep the data of the array safe in case when one of the drives crushes, we “simulated” a failure of one HDD in RAID1, RAID5 and RAID 10 arrays. The imitation was simple, as in the review of the Intel SRCS14L controller: we unplugged the power cable from the hard disk drive and tracked the array status from the Adaptec Storage Manager (Browser Edition) utility.
It took quite a bit of time for the array to be restored while still responding to users’ requests so I removed all workload from the controller (i.e. terminated the benchmark) and noted the time it took the controller to restore the array.
So the controller restored the data integrity in:
- 34min with the RAID1;
- 82min with the RAID5;
- 69min with the RAID10.