Jon Lowrey wrote:
I've executed the well documented (and completely unsupported) "defaults write com.apple.systempreferences TMShowUnsupportedNetworkVolumes 1" system hack to enable me to use TM to backup to unsupported network volumes, but it doesn't work!
I'm trying to use an external 500gb USB formatted as FAT and also FAT32 and TM still won't recognise it.
That's correct. TM will only back up to a drive with either +Apple Partition Map+ or
GUID *Partition Map Scheme,* and either +Mac OS Extended (Journaled)+ or +Mac OS Extended (Case-sensitive, journaled)+
Format.
Is there something I am missing? I am trying to use the same disk, with one partition, for my TM backup and occasional use for the odd Windows file.
That's not going to work.
What you
might be able to do, is make two partitions on the drive, one for TM and one for the other stuff. That's recommended any time you're going to put other data on the drive, since TM will, by default, use up all the space available to it before it starts deleting old backups to make room for new ones.
See #3 and #5 in the
Frequently Asked Questions *User Tip,* also at the top of this forum.
But if this is a network drive, Time Machine may not work at all, even with the "hack." If you need the "hack," you're taking a risk:
From a post in another forum (found by V.K.):
The technical reason why Apple limits Time Machine to 10.5 AFP volumes appears to be to prevent disk image corruption. There were additional features added to AFP in 10.5 to support Time Machine. These presumably allow the disk image engine to force disk image journal data to write out all the way to the disk. Without such features, a network interruption can result in a corrupted filesystem on the disk image despite journaling. Remember, journaling relies on the journal being written all the way to disk before the changes take place. If you can't guarantee that (e.g., because of network/NAS buffering) then the journal is useless. Time Machine appears to rely heavily on disk journaling to deal with network drop-outs, interrupted backups, and the like. Take this away and your data is at risk.
If the NAS you are using supports these features it should report them to the OS and you should natively be able to choose that volume. If you have to trick the OS to use the volume it means the NAS does not support it.
To summarize: if you care about your backup data you should avoid using non-natively supported AFP servers.
That post obviously applies to Leopard; Snow Leopard appears to have added some requirements, that are also not supported by all NAS devices, and some that were working with Leopard no longer work with Snow Leopard.
