SamyGO

Since I have no access to the link I can not even literate.
Is there a guide to PVRAnyDev? My knowledge of Linux is still not very large.

Use SamyGO Extensions and enable startup script of PVRAnyDev
viewtopic.php?f=63&t=6778

What I have to do after that?

check, maybe you get nfs recording scripts working out of the box? All included, but not tested on F series yet.

So I have to create a Virtual USB device mounted with an NFS-directory and test to record on it?

you have to read more, related topics here.

Could you please post some links to posts / topics in which I should immerse myself?

have a look at c-series wiki, basically its only a few scripts that do the magic, there haven't been big changes since this afaik

i advice you just enable all remi71 scripts, adapt variables and i guess you have big chance for success.

Some links (yes, not from F series, but doesn`t mater, it works on D and E series as well, info is universal, SamyGO Extensions are just slightly modified).
http://wiki.samygo.tv/index.php5/PVR_Re ... r_C-Series
viewtopic.php?f=12&t=1332#p11570
viewtopic.php?f=24&t=5269
viewtopic.php?f=52&t=5929#p42591
viewtopic.php?f=9&t=4972
viewtopic.php?f=25&t=3897

and... this...:
viewtopic.php?t=7007&p=53072#p52688

p.s. What i definitelly know, on F series must be used ext4 filesystem, NOT xfs. This is only noticed difference. But if you start PVRtoAny patch, then this doesn`t matter.

oh, i already had forgotten this: viewtopic.php?f=9&t=4972
its not about the total speed you achieve with dd if=/dev/zero testing, its about constant data stream and also quality of nfs service

downside of the medal, it could be hard to monitor this on a dedicated NAS device...