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I have an external 1.5TB HDD which I would like to use as a backup for both my Mac (OSX 10.5.7) and PC (Windows Server 2003). If possible, I would like to utilize Apple's built in Time Machine for the Mac backups and then use another tool (any recommendations?) on the PC to do incremental backups every so often.

Now, I've setup the HDD on the Mac with Time Machine and ran it. I then plugged the drive into the PC and using MacDrive (demo license), manually copied some files to backup just to test out. I plugged this HDD back into the Mac to see if it would be working and I got a disk not initialized error.

Any tips or ideas on how I can get around this or set it up some other way.

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Are they on the same network? You could share the drive on the Mac and have the PC backup over a local network connection (I have my Mac and PC directly connected together for such a purpose.)

You could also possibly partition the drive into an NTFS partition (for your PC) and a HFS partition (for your Mac Time Machine.)

As far as backup software for the PC, it depends if you want the software to do a full backup including the OS, or if you want to to just backup your documents and the like. (The latter would work great with Unison or rsync.)

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I think he's using it as local storabe (USB or firewire) – Server Horror Jun 10 '09 at 5:12

The only filesystems that are readable on the major OSs and their variants are ISO9660 and FAT to my knowledge. With a 1,5TB harddisk you will have a problem I think. I remember some border on the FAT partition size and that was definitely below 1500GB

I'd rather use some network attached storage to accomplish what you want. Cheap disks with network functionality are available at your local retailer.

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FAT32 can handle volumes up to 2Tb (8Tb technically, but I don't know if any implementations support >2Tb) and is supported by all modern OS variants (Windows, Linux, BSD, OSX, ...). See Since Windows 2000 the Windows formatter will refuse to format a FAT32 partition larger than 32Gb, but Windows 98/ME/2K/XP/2K3/Vista/2K8/7 will reliably use a bigger volume if created elsewhere (i.e. by OSX). This may be the size limit that you are remembering. Also, no individual file can be 4Gb or larger on a FAT32 filesystem. – David Spillett Jun 10 '09 at 11:08
That sounds like it. Someone vote me down for the incorrect answer :) – Server Horror Jun 10 '09 at 11:29

I can't think of any solution that supports both properly without some kind of bodge, and the idea of "some kind of bodge" being near "backups" makes me sad :-(

Best ideas are either backup to the Mac across the network for the Windows machine as Rizwan suggests, or failing that just buy a second drive - not what you wanted to hear but it isn't that expensive in the great scheme of things and certainly "cheaper" in terms of your sanity than a backup solution you can't quite trust.

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You have two possible ways of share a disc between a Windows machine and a Mac and use it to backup both machines:

  1. Connect the disc to your Mac, configure Time Machine. Then share the disc through SAMBA so the Windows machine can see it. Practically every backup utility in Windows can do backups using network shares.
  2. Connect the disc to your windows machine and share the disc. From your Mac you can mount the shared disc and configure Time Machine to use the network shared disc to do the backups. You can find a simple tutorial about this on the following web:

In both cases you need you two machines to be network connected.

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