At Vastspace, we insist on only SAS Hard Drives or Enterprise SSDs for our servers. It’s because SAS Hard Drives are the most reliable, maintain their performance under more difficult conditions, and perform much better than compares to either Near Line SAS or SATA disks.
In reliability, SAS hard drives are an order of magnitude safer than either Near Line SAS or SATA disks. The metric is measured in bit error rate (BER), or how often bit errors may occur on the media. With SAS hard drives, the BER is generally 1 in 10^16 bits. Read differently, that means you may see one bit error out of every 10,000,000,000,000,000 (known as 10 quadrillion) bits. By comparison, SATA drives have a BER of 1 in 10^15 (1,000,000,000,000,000 or 1 quadrillion). Although this does make it seem that SATA disks are pretty reliable, when it comes to absolute data protection, that factor of 10 can be major.
SAS hard drives are also built to more exacting standards than other kind of hard drives. SAS hard drives have a mean time between failure (MTBF) of 1.4 million hours or higher compared to 1 million hours or lower for most SATA hard drives.
Here’s a good article on Choosing Between SAS vs. SATA Hard Disk for Your Server RAID System from Intel: http://download.intel.com/support/motherboards/server/sb/enterprise_class_versus_desktop_class_hard_drives_.pdf