I have a ReadyNAS Duo, and several Mac devices backing up to it (via the typically “Apple awesome” Time Machine feature).
I recently upped the allocated disk space in FrontView to 300GB, from 120GB – which while each Mac’s Time Machine preferences said “NAS device, 300GB” – claimed the disk didn’t have enough “temporary space” to perform the backup.
Hmm.
I got SSH access to the ReadyNAS working – (I used Enable SSH plugin), and took a look around the filesystem.
It appears in classic OSX style, Apple have opted for a simple .plist info file:
cat /c/.timemachine/Matthew\ Hall’s\ MacBook.sparsebundle/Info.plist
...
<key>size</key>
<integer>107374182400</integer>
...
Upping the value to the match the new disk size (300*1024*1024*1024), solved the issue.
Presumably (speculation) OSX treats the .sparsebundle directory as a disk image – and the Info.plist defines how “big” the disk image is – even though its a directory (can anyone confirm?). Thus the “disk” was indeed 300GB, but the existing backup image was only 100GB …
Shame Netgear / Apple didn’t put something obvious to allow updating the .plist file, but never mind! Problem solved …