I have a question for the knowledge and many years of experience gathered here :-)
Well, we want to set up a new NAS filer:
I remember that RAID sets should not exceed 12 - 16 disks + parity disks: Do any of you know where this statement comes from? Is there any paper where the influence of RAID set sizes has been examined?
Second question: It has also been stated that RAID-6 systems decrease dramatically in performance from approx. 50% fill level. This is new to me. Can any of you confirm this? Or is this perhaps due to too many disks in the RAID set?Thank you!

Dear Bjørn

Array Sizes are experienced from the field. On the one hand more drives will increase the netto/brutto relationship and the price, you will pay. Also will increase the performance of the array. On the other hand the probability of a drive failure will also increase dramatically with each drive added, also doubledisk failure probability, so you will have to find the "sweepspot". Each vendor does this in different ways and results, so i did not recognize that numbers directly. I think you are familiar with the Array setting in the FlashSystems. Default with DRAID6 is 10+P+Q, but it is possible to increase the grouping algorythm to 14+P+Q.
To your secon question : I have heard from my partners, that systems of a competitor, famous for NAS Filers, will decrease performance when the data stored is reaching capacity limit. If this behavour is related to the Servercomponent in the NAS or related to the underlaying Blockstorae array, i can not answer generally.