On Fri, Jun 3, 2016 at 7:51 PM, Christoph Anton Mitterer <cales...@scientia.net> wrote:
> I think I remember that you've claimed that last time already, and as > I've said back then: > - what counts is probably the common understanding of the term, which > is N disks RAID1 = N disks mirrored > - if there is something like an "official definition", it's probably > the original paper that introduced RAID: > http://www.eecs.berkeley.edu/Pubs/TechRpts/1987/CSD-87-391.pdf > PDF page 11, respectively content page 9 describes RAID1 as: > "This is the most expensive option since *all* disks are > duplicated..." You've misread the paper. It defines what it means by "all disks are duplicated" as G=1 and C=1. That is, every data disk has one check disk. That is, two copies. There is no mention of n-copies. Further in table 2 "Characteristics of Level 1 RAID" the overhead is described as 100%, and the usable storage capacity is 50%. Again, that is consistent with duplication. The definition of duplicate is "one of two or more identical things." The etymology of duplicate is "1400-50; late Middle English < Latin duplicātus (past participle of duplicāre to make double), equivalent to duplic- (stem of duplex) duplex + -ātus -ate1 http://www.dictionary.com/browse/duplicate There is no possible reading of this that suggests n-way RAID is intended. -- 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
