rsync as a backup solution

Ian! D. Allen [NCFreeNet] idallen at
Wed Jun 5 22:50:15 EST 2002

Be aware that with any "live" backup solution your backup directory
may be corrupt in subtle ways.  We've been running rsync for years now
to back up Windows files stored on our Samba server, and we often find
files on the backup destination that have the identical date and time
stamp as the source but different content.

I suspect that, since Unix only records file times to the second (and
Windows only to every two seconds), a file was being changed while rsync
was reading it.  Rsync copied the data from the file and, in the same
second, the user overwrote part of the file with new data.  The result -
two files that have the same size, date, and time but different data.

Unless you call rsync with the --ignore-times option next time, this
error will go undetected by subsequent rsync runs.

-IAN!  Ian! D. Allen   Ottawa, Ontario, Canada   idallen at
       Home Page on the Ottawa FreeNet:
       College professor at:
       Board Member, TeleCommunities CANADA

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