Finally I managed to perform network Time Machine backups.
Despite the fact that network Time Machine backups were advertised by Apple before Leopard launch, this functionality has been disabled just before the release. I don't want to speculate about true reasons behind this move. There are some rumors that it was because of new apple's Time Capsule product and an attempt to bind network backups of Mac OS X to this device. Could be partially, however problem seems to be technical, not economical.
Network TM backups are disabled by default, however turning this feature on is quite simple, it is enough to run in Terminal:
defaults write com.apple.systempreferences TMShowUnsupportedNetworkVolumes 1
In my case one more required step was to create sparse image bundle for the backup named in pattern
hostname_mac address without separators
, on the destination backup share.
(Update: you might be interested in precise command for creating sparse image bundle.)
This kind of backup use to be potentially unstable - there is an apple forum post regarding this issue. The problem seems to be fixed now with the latest TimeMachine and AirPort update. Probably this bug was an original rationale behind disabling network TM backups when the Leopard was released. Are there any more obstacles for network TM backups? If not - apple, please make network volumes appear in TM's drive chooser by default. Also the need of preparing sparse image bundle in order to make a backup seems to be too difficult for many Mac OS X users. Is it made for purpose? I believe there is still some technical issue behind. The only thing that worries me is backup instability. :(