On Tue, Aug 04, 2026 at 02:00:05PM -0400, Stefan Monnier wrote:
So overall the circumstances where raid 5/6 makes sense are a small minority. It's mostly for cases where total capacity is a lot more important than performance and even there, the benefit is only 33% in your scenario (8GB vs 6GB). And when total capacity is a lot more important than performance one would typically go for HDDs (where the performance impact of raid 5/6 tend to be even more pronounced).
That depends on what you mean by "performance". A large (8 or more drive) RAID-6 is going to have similar performance to RAID-10 for random or sequential reads (operations will be balanced across drives). For sequential writes the RAID-6 will likely be faster. Random writes will be worse on the RAID-6, but a write cache will hide much or all of that depending on the details of cache size, write size, etc. And with larger numbers of drives the difference in overhead becomes more significant. (50% usable for RAID-10, 75% for 8 drive RAID-6, 83% for 12 drive RAID-6.) And a last really important feature: RAID-6 can tolerate *two* failed drives in an array without losing data. With RAID-10 if a drive fails during a rebuild, the array is done. And rebuilds can take a *long* time (like, days). You can get double disk failure tolerance on RAID-10, but then you're down to 33% usable space.
