On 28/02/18 21:21, Wol's lists wrote:
Let's say I decide to be intentional about building a 80TB usable LV with your setup. If I use 10TB drives, does that mean I'd have to buy 33 x 10TB drives.At $400/drive, that's $13.2K just for the drives (chassis, controllers, etc not included). That seems like a lot of money for 80TB useable.
I'm trying to remember my maths. That's 8 drives for data plus 2 parity, twice. 20 drives. You would need either 21 or 41 drives. But 41 sounds wrong, it should certainly work with 31. It should be possible to do it with 21, maybe I just need to improve my algorithm.
I think I've sussed what was up with my brain-fade - I'm getting my logical and physical drive sizes mixed up. If we created our raid-61 as a 7,2 with let's say 22 drives, that would splatter 14 logical 16(ish) tera drives across 22 physical 10tera drives. Adding a new physical drive would increase the size of each logical drive by 7-800gig. At the end of the day this is all trade-offs - there comes up a point where things don't add up because you've got too few drives (you might need to go 6,2 to get the non-pathological algorithm which increases your need for drives because of the increased parity etc etc), or the number of drives might be so high as to be unmanageable. This algorithm was really conceived for arrays with about 100 disks! Cheers, Wol -- To unsubscribe, e-mail: opensuse+unsubscribe@opensuse.org To contact the owner, e-mail: opensuse+owner@opensuse.org