On Sat, 2016-06-04 at 11:00 -0600, Chris Murphy wrote: > SNIA's DDF 2.0 spec Rev 19 > page 18/19 shows 'RAID-1 Simple Mirroring" vs "RAID-1 Multi- > Mirroring"
And DDF came how many years after the original RAID paper and everyone understood RAID1 as it was defined there? 1987 vs. ~2003 or so? Also SINA's "standard definition" seems pretty strange, doesn't it? They have two RAID1, as you say: - "simple mirroring" with n=2 - "multi mirrioring" with n=3 I wouldn't see why the n=2 case is "simpler" than the n=3 case, neither why the n=3 case is multi and the n=2 is not (it's also already multiple disks). Also why did they allow n=3 but not n>=3? If n=4 wouldn't make sense, why would n=3, compared to n=2? Anyway,... - the original paper defines it as n mirrored disks - Wikipedia handles it like that - the already existing major RAID implementation (MD) in the Linux kernel handles it like that - LVM's native mirroring, allows to set the number of mirrors, i.e. it allows for everything >=2 which is IMHO closer to the common meaning of RAID1 than to btrfs' two-duplicates So even if there would be some reasonable competing definition (and I don't think the rather proprietary DDF is very reasonable here), why using one that is incomptabible with everything we have in Linux? Cheers, Chris.
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