This whole thing about hard links got me curious and I did some Googling. Here’s an excerpt from an old article on Ars Technica <https://arstechnica.com/gadgets/2011/07/mac-os-x-10-7/12/> that states pretty clearly what I think.
> One particularly scary example is the implementation of hard links > <http://arstechnica.com/apple/2007/10/mac-os-x-10-5/14/#symlinks-and-hard-links> > on HFS+. To keep track of hard links, HFS+ creates a separate file for each > hard link inside a hidden directory at the root level of the volume. Hidden > directories are kind of creepy to begin with, but the real scare comes when > you remember that Time Machine > <http://arstechnica.com/apple/2007/10/mac-os-x-10-5/14/> is implemented using > hard links to avoid unnecessary data duplication. > > Listing the contents of this hidden directory (named "HFS+ Private Data", but > with a bunch of non-printing characters preceding the "H") on my Time Machine > backup volume reveals that it contains 573,127 files. B-trees > <http://developer.apple.com/legacy/mac/library/technotes/tn/tn1150.html#BTrees> > or no b-trees, over half a million files in a single directory makes me > nervous. > > That feeling is compounded by the most glaring omission in HFS+—and, to be > fair, many other file systems as well. HFS+ does not concern itself with data > integrity. The underlying hardware is trusted implicitly. If a few bits or > bytes get flipped one way or the other by the hardware, HFS+ won't notice. > This applies to both metadata and the file data itself. > > Data corruption in file system metadata structures can render a directory or > an entire disk unreadable. (For a double-whammy, think about corruption that > affects the "HFS+ Private Data" directory where every single hard link file > on a Time Machine volume is stored.) Corruption in file data is arguably > worse because it's much more likely to go undetected. Over time, it can > propagate into all your backups. When it's finally discovered, perhaps years > later when looking at old baby pictures, it's too late to do anything about > it. > --- Lee Larson [email protected] <mailto:[email protected]> … we are all in the gutter, but some of us are looking at the stars. — Oscar Wilde, Lady Windermere’s Fan
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