On Sat, Jun 4, 2016 at 11:37 AM, Christoph Anton Mitterer <cales...@scientia.net> wrote: > 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?
mdadm supports DDF. -- Chris Murphy -- To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
