I would say this is a tradeoff between space overhead (2 parity disks per array) and data reliability (mean time before data loss, MTBDL, or MTTF). Space overhead is easy to calculate. For MTBDL, there are various of documents online, for example: https://jontse.com/courses/files/cornell/ece5730/Lecture24.pdf For your questions: > a) recommended number of disks included in RAID array set? I would personally recommend 12 to 15 HDDs per array. > b) Is it possible to include all 84 disks in one array and leave 2 of them as host spare? It is possible, but not recommended. 84 disks per array really hurts reliability. > c) Is there a raid6 best practices document to refer to ? I am not aware of such documents. Hope these help. Song -- To unsubscribe from this list: send the line "unsubscribe linux-raid" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
