So under Apple’s new file structure what backup will protect the integrity of the data? This article talks about HFS+ but for those with High Sierra and a SSD now implementing APFS, what works with this format?
John > On May 7, 2018, at 11:41 AM, Lee Larson <leelar...@me.com> wrote: > > 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://urldefense.proofpoint.com/v2/url?u=https-3A__arstechnica.com_gadgets_2011_07_mac-2Dos-2Dx-2D10-2D7_12_&d=DwIFaQ&c=OAG1LQNACBDguGvBeNj18Swhr9TMTjS-x4O_KuapPgY&r=F2GFXrjLFqVo3VwvIlo_XYeEiRRjHv15rxcenz7A21woG2aFGcrzndoSsskxfmOs&m=d-1_IOwJ8B4vupKVHlD6ajtMQGKDWWnUBZUi_acPEH8&s=6GcJrewHIO7QzZpCEyYE_SCKj5IK22_FlJ42YEjYI7M&e=> > that states pretty clearly what I think. > > >> One particularly scary example is the implementation of hard links >> <https://urldefense.proofpoint.com/v2/url?u=http-3A__arstechnica.com_apple_2007_10_mac-2Dos-2Dx-2D10-2D5_14_-23symlinks-2Dand-2Dhard-2Dlinks&d=DwIFaQ&c=OAG1LQNACBDguGvBeNj18Swhr9TMTjS-x4O_KuapPgY&r=F2GFXrjLFqVo3VwvIlo_XYeEiRRjHv15rxcenz7A21woG2aFGcrzndoSsskxfmOs&m=d-1_IOwJ8B4vupKVHlD6ajtMQGKDWWnUBZUi_acPEH8&s=FuDfczjyITunXFrc14l3oGEL6NyPI6h7gqkA2WqSv6Q&e=> >> 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 >> <https://urldefense.proofpoint.com/v2/url?u=http-3A__arstechnica.com_apple_2007_10_mac-2Dos-2Dx-2D10-2D5_14_&d=DwIFaQ&c=OAG1LQNACBDguGvBeNj18Swhr9TMTjS-x4O_KuapPgY&r=F2GFXrjLFqVo3VwvIlo_XYeEiRRjHv15rxcenz7A21woG2aFGcrzndoSsskxfmOs&m=d-1_IOwJ8B4vupKVHlD6ajtMQGKDWWnUBZUi_acPEH8&s=8JSOIpxxE2q9Y5YAfmnaylCj2QMRUcYMgSuq6M99yA4&e=> >> 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 >> <https://urldefense.proofpoint.com/v2/url?u=http-3A__developer.apple.com_legacy_mac_library_technotes_tn_tn1150.html-23BTrees&d=DwIFaQ&c=OAG1LQNACBDguGvBeNj18Swhr9TMTjS-x4O_KuapPgY&r=F2GFXrjLFqVo3VwvIlo_XYeEiRRjHv15rxcenz7A21woG2aFGcrzndoSsskxfmOs&m=d-1_IOwJ8B4vupKVHlD6ajtMQGKDWWnUBZUi_acPEH8&s=RgnSk3yYIbcr0sVn0SjzWyH9TqUqhGOTueD0vg-6sY4&e=> >> 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 > leelar...@me.com <mailto:leelar...@me.com> > > > … we are all in the gutter, but some of us are looking at the stars. — > Oscar Wilde, > Lady Windermere’s Fan > > _______________________________________________ > MacGroup mailing list > Posting address: MacGroup@erdos.math.louisville.edu > Archive: > <https://urldefense.proofpoint.com/v2/url?u=http-3A__www.mail-2Darchive.com_macgroup-40erdos.math.louisville.edu_&d=DwIFaQ&c=OAG1LQNACBDguGvBeNj18Swhr9TMTjS-x4O_KuapPgY&r=F2GFXrjLFqVo3VwvIlo_XYeEiRRjHv15rxcenz7A21woG2aFGcrzndoSsskxfmOs&m=d-1_IOwJ8B4vupKVHlD6ajtMQGKDWWnUBZUi_acPEH8&s=HoU-j3_jHFqAltPqHxeFsqL5GqA2YutMHqU0K3tUbGA&e=> > Answers to questions: <http://erdos.math.louisville.edu/macgroup/>
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