Monday, February 4, 2013

Robocopy to NAS (FFT)

robocopy is a nice command prompt utility for backup files.  You can configure it to only copy files that are newer (based on timestamp) to save time and bandwidth when you are doing backup.  However, there seems to be a problem when it is backing up files from NTFS filesystem to other filesystem, e.g. ext4, XFS etc commonly found in NAS.  It seems time granularity of time value can causes robocopy mistreats files.  That is robocopy may treat identical files as different because it thinks one of them is newer.  Luckily, this can easily be fixed by use the /FFT swtich.  Full explanations can be found at this link

http://www.conetrix.com/Blog/post/Robocopy-Incorrectly-Detects-Files-as-Newer-When-Copying-Between-Different-File-Systems.aspx

Hence, the robocopy command I would use is:

robocopy [source directory] [target directory] /MIR /Z /DCOPY:T /FFT