Can't copy files to NAS anymore

Question

I'm usign a NAS from WD to store some files (http://www.wdc.com/de/products/Products.asp?DriveID=587).

I'd worked without problems for hours, but suddently some hours ago I can't copy any files to the disk anymore. If I try, the following error occurs:

You need permission to perform this action.

I don't really know why this happens, since I didn't changed anything. However if I look at the properties of various folders on the NAS, it says read-only. However if I try to change that, the same error occurs. Does anybody know how to solve this??

EDIT: If helpful, here the current available space:

Total amout of disc space:        957,439,436K
Available disc space:              98,843,144K
Available disc space (percent):      10%

Could this be a problem?

EDIT 2: I already tried to reboot both the computer and the NAS. Didn't improved the actual situation.

Currently I'm using Windows Vista Enterprise and I'm accessing the NAS over the local network.

Answer 1

You need permission to perform this action.

Hmm... that sounds familiar.

Total amout of disc space:        957,439,436K
Available disc space:              98,843,144K
Available disc space (percent):      10%

If your NAS is one of the usual linux boxen, filling up to 90% may have the "root only" limit kicked in. This prevents any ordinary user from filling a HDD (partition) completely.

Filling a disk over ~90% has also very bad effects on performance. The data is scattered all over the disk - very many head movements are needed for both reading and writing => The performance lowers almost to a grinding halt. And NAS boxen have typically NO defragmentation.

Simple solution: Try to delete some data...