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    5 Star Lounger st3333ve's Avatar
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    Time change messes incremental backup (XP Pro SP2)

    I run a batch file at the end of each day that uses several Robocopy commands to do an incremental backup (to a CD-RW disk) of the files created or changed that day in a number of different directories.

    It works fine except when we go through a time change (and maybe only the spring change, and not the fall change). On the evening of April 2 (the first run after the change to DST), Robocopy decided that every relevant file on my hard drive was a newer version than the copy already on the CD-RW disk, and so a long non-incremental backup resulted. I remember this happening in connection with at least one previous time change, although I can't remember whether it was last fall or last spring.

    Anybody else had a similar experience, or know what WinXP does with respect to DST that causes this unwelcome side effect?

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    Re: Time change messes incremental backup (XP Pro

    I didn't have a great problem, perhaps because my home installation is fairly static.

    ROBOCOPY did a bit more work in my daily mirroring of C: to my external drive (4000 files were copied instead of 1000 or so).
    SyncToy had a specific update very recently to make itself DST-aware.
    Of course NTBackup on my 2003 server was no different from normal since it does a complete backup every time!

    A quick Google search shows that the Vista version of ROBOCOPY (which will be 'built-in' to Vista!) has a new switch<pre>/DST :: compensate for one-hour DST time differences.</pre>

    It took them all that time?!

    John
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  3. #3
    5 Star Lounger st3333ve's Avatar
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    Re: Time change messes incremental backup (XP Pro

    Thanks for the input, but I'm afraid I'm still in the dark. What time-change behavior will the /DST switch be compensating for? When Windows does its DST thing, it doesn't change the modified date/time of the existing files on the PC -- an assumption I just verified by checking a CD-R backup from the end of January -- a file on my hard drive with a modified date/time (as of today) of 1/16/06 11:10 a.m. also shows as 1/16/06 11:10 a.m. on the end-of-January CD-R.

    So I still don't understand what Windows does that causes Robocopy to think all the unchanged files on the hard drive have become "newer" than the backup copies on my CD-RW disk. <img src=/S/shrug.gif border=0 alt=shrug width=39 height=15>

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    Re: Time change messes incremental backup (XP Pro

    There's another thread this year on the topic, <post#=567,324>post 567,324</post#>, which might be worth a look? There are more references there...

    John
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    5 Star Lounger st3333ve's Avatar
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    Re: Time change messes incremental backup (XP Pro

    Thanks for the link. I skimmed the File Times article until my head started to hurt. I think I read enough to understand that there's no simple tweak I can perform to avoid this once-a-year too-much-backup inconvenience (at least until I start using the Vista version of Robocopy).

    I find it a little curious that Windows Explorer doesn't reflect the same "interpreted" date/times that Robocopy uses to determine whether a file on CD is "newer" than the copy on the hard drive.

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