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DavidHertzberg

PSA: Wikipedia article on Retrospect going away in current form

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Getting back to the latest problems with the Wikipedia articles, DovidBenAvraham has done further work—which Pi314m has left alone so far.  It looks as if the fact that other WP editors, who may be administrators, took DBA's side in the latest Request for Comments has at least temporarily persuaded Pi314m to go mess with some other articles instead.

Actually it now appears that Pi314m's heart was in the right place when he merged the "Continuous Data Protection" article into the "Backup" article.  The difficulty is that there are two types of backup applications that are called "CDP".   One is "true CDP", which was invented in 1989 but is only implemented in a handful of applications.  "True CDP" applications must get their "fingers" into an OS filesystem at the level where actual disk writes take place; they do so either by requiring that the OS be run inside a virtual machine so that they can get their "fingers" into the VM, or by requiring that special disk driver software with built-in "fingers" be installed.  "True CDP" backup can restore interactive applications to precisely the point where the system failed, but they're too expensive in money and complications for ordinary home/SME installations.   R. V. (whose spelled-out name I am forbidden to mention on these Forums) may be a "true CDP" backup application, but I can't tell.

Much more common and less expensive are "near-CDP" backup applications, which were introduced after the front 7 screen pages of the "Backup" article were written.  AFAIK the first of these was Apple's Time Machine, which automatically does an incremental backup once an hour without a script.  They are made possible by intent-logging features that are now in all commercial OSs' filesystems, and are made non-burdensome by "snapshotting" facilities that are also in such filesystems (at long last for Apple's APFS, which was introduced at least partly because Apple couldn't bolt "snapshotting" onto its older HFS+).  "Near-CDP" backup applications can with proper add-ons restore interactive applications to the last point at which an incremental backup was done, possibly as little as 10 minutes ago, which is close enough for Microsoft Exchange and some database applications.  Retrospect non-V. can backup hourly, if you schedule a script accordingly, but it doesn't (so far) do so from "snapshots"  (not to be confused with Retrospect Snapshots, which are a different feature named a decade before the industry-wide OS feature appeared—at which point EMC dropped the use of the term Snapshot with Retrospect Mac 8 but not with Retrospect Windows).

So DBA had to write three different versions of the above exposition.  The first version revises the re-established "Continuous Data Protection" article, with added quotes from the references because Pi314m evidently can't read technical English at a senior-high-school level (possibly as a result of his apparent sub-culture, in which boys past the age of 13 are educated—without any math or science classes—almost entirely in a non-modern European language).  The second version is the "Near-CDP" sub-subsection of the "Backup" article, which omits everything but a mention of "real CDP" because ordinary readers will never encounter it.  The third version is the "Backing up interactive applications via true Continuous Data Protection" paragraphs of the "Enterprise client-server backup" article, which can omit any mention of "near CDP" because it refers readers to the "Continuous Data Protection" article.

 

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