FAT32/NTFS mounts are read only on FreeNAS. From the FreeNAS FAQ on the topic:
Q: Can I use an NTFS, FAT, or EXT formatted drive with FreeNAS?
A: Yes you can, but there are limits:
- FAT, NTFS and EXT2/3 can be used to
transfer bulk data to a UFS formatted
- FAT, NTFS and EXT2/3
should be used in read-only mode, not
- Only EXT2/3 revision 0
with Inode size of 128 bytes
supported. Revision 1 uses a inode
size of 256 bytes which is not
supported by FreeBSD. Creating ext2/3
partitions, using 128 bytes via ”-I
128” could solve this problem but the
file system is permanently in “not
UFS is the native FreeNAS file system, it is robust, stable and we recommend you use it. You can use other file systems in read/write mode, but this is not recommended.