+=head2 What type of storage space do I need?
+
+BackupPC uses hardlinks to pool files common to different backups.
+Therefore BackupPC's data store (__TOPDIR__) must point to a single
+file system that supports hardlinks. You cannot split this file
+system with multiple mount points or using symbolic links to point a
+sub-directory to a different file system (it is ok to use a single
+symbolic link at the top-level directory (__TOPDIR__) to point the
+entire data store somewhere else). You can of course use any kind of
+RAID system or logical volume manager that combines the capacity of
+multiple disks into a single, larger, file system. Such approaches
+have the advantage that the file system can be expanded without having
+to copy it.
+
+Any standard linux or unix file system supports hardlinks. NFS mounted
+file systems work too (provided the underlying file system supports
+hardlinks). But windows based FAT and NTFS file systems will not work.
+
+Starting with BackupPC 3.1.0, run-time checks are done at startup and
+at the start of each backup to ensure that the file system can support
+hardlinks, since this is a common area of configuration problems.
+