Will I see a write performance increase going from single disk to CentOS Software RAID10? Any industry estimates on the % increase?
RAID 10 provides both reliability and performance by mirroring and striping.
RAID 10 can provide up to N/2 in performance, both throughput and IO, where N is the number if drives in array, capacity will be about 1/2 of total. i.e. in case of 10 drives of 500GB capacity it can provide up to 500% of performance of single drive and ca. 2.5 TB of array capacity and can sustain failure of up to 5 drives (if drives do not share same segments).
RAID 10 requires at least 4 drives (2-drive RAID 10 actually is RAID 1, 3-drive RAID 10 is RAID 1E).
Linux kernel RAID (mdraid) implements three layouts of placing chunks, each of them have impact on performance, imbalance between Read and Write in case of non-linear, random operations.