Based on Changing a RAID-10 into a RAID-5
It is usually assumed that the best HDD organization on a backup server is a RAID5, since it provides a fairly good price/volume. Unfortunately, increasing of disk count affect to some RAID5 disadvantages, in particular the in reliability and recovery speed. For example if the server has RAID5 of 6 (six) SATA disk drives (even it’s reliable enough, such as WD Re), with one disk replacement, array recovery time is about 10 hours (in my case). At the recovery time reservation is absent, the load on the disks are increased, that increases the probability of failure of the remaining disks, and if all the disks have same series, the probability of another disk will deteriorate during the recovery, increase even more.
In this regard, it was decided to convert the existing disk array from RAID5 to RAID10 with the addition of two drives, that in theory should lead to increasing of server performance and improving reliability.