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I have two disks, D:\ with 70gb capacity and E:\ with 250gb

I want EVERYTHING that is added, modified, deleted etc to E:\Backups\ to be mirrored onto D:\

How to do? I'm running Win XP pro. Both disks are SATA.

I would prefer to not create any partitions because E:\ is already filled. But if it's possible to split partitions and this makes mirroring a lot easier this might also be a good option.

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Can you explain why you'dd like to create a mirror? – Dimitri C. Sep 2 '09 at 10:27
In case any of the disks crashes. – ugh Sep 2 '09 at 12:00
up vote 1 down vote accepted

an automatic file synchronization utility

Take a look at Robocopy, it should be perfect for this (under XP, you have to download it).

robocopy, or "Robust File Copy", is a command-line directory replication command. It was available as part of the Windows Resource Kit, and introduced as a standard feature of Windows Vista and Windows Server 2008. (

Something like this:

robocopy D:\ E:\ /LOG:C:\robo.log /R:0 /W:0 /E /IT /MIR

You can use the link above to look for other parameters or simply type "robocopy /?" in your command line for help.

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RAID 1 would not be a solution at all since both disks are of different sizes. The best solution for you would be to run an automatic file synchronization utility - I recommend Unison.


Set Unison to synchronize E:\Backups*.* to D:\, and let it run automatically. In order to minimize system performance loss, you might want to set Unison to synchronize at periodic time intervals - achieving a balance between performance and up-to-date backups.

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RAID isn't an answer here, as you're looking at mirroring just a folder, and not an entire drive, also as your drives are different sizes you'll lose the extra capacity on the larger drive.

Have you tried Microsoft SyncToy (ignore the "Toy" part of the name, that's just because it was branded with the PowerToys downloads at one point). Although it's distributed by the MS ProPhoto Group, it happily syncs any file type.

I use it to backup selected folders on my hard drive to a couple of different external USB drives, but its just as happy with syncing internal drives, even happily copes if either drive changes drive letter for any reason.

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I think RAID mirroring is not a good backup solution. A harddisk crash is far from the only possible cause of data loss. Examples of other hazards:

  • files modified/deleted by mistake (human error)
  • a computer virus modifying/deleting files
  • a bug in an application deleting the wrong files
  • burglary
  • fire
  • electrical surge (for example a lightning stroke). As both of your mirrored disk are built in the same system, it is likely they both will be damaged at the same time.

I think a better solution would be to buy an external harddisk which you keep disconnected, and use specialized backup software (I use Second Copy) to update the backup every once in a while, keeping multiple versions of your files.

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