Hi all, I'm playing around with RAID-6 algorithms lately. With RAID-6 I mean a setup which needs N+2 disks for N disks worth of storage and can handle any two disks failing -- this seems to be the contemporary definition of RAID-6 (the originally proposed "two-dimensional parity" which required N+2*sqrt(N) drives never took off for obvious reasons.) Based on my current research, I think the following should be true: a) write performance will be worse than RAID-5, but I believe it can be kept to within a factor of 1.5-2.0 on machines with suitable SIMD instruction sets (e.g. MMX or SSE-2); b) read performance in normal and single failure degraded mode will be comparable to RAID-5; c) read performance in dual failure degraded mode will be quite bad. I'm curious how much interest there would be in this, since I certainly have enough projects without it, and I'm probably going to need some of Neil's time to integrate it into the md driver and the tools. -hpa -- <hpa@transmeta.com> at work, <hpa@zytor.com> in private! "Unix gives you enough rope to shoot yourself in the foot." http://www.zytor.com/~hpa/puzzle.txt <amsp@zytor.com> - To unsubscribe from this list: send the line "unsubscribe linux-raid" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
