[OpenAFS] Network becomes terribly slow when cache manager flushes updates over xDSL

[Goulou]

Hi all,=20

I'm trying to give my users an access to their home directory over the Inte=
rnet, so they can connect to there account from their homes (place, not dir=
ectory...).
Unfortunately, my tests show that when a large update occurs to the disk (f=
or example, the user download a file and puts it in any directory, or makes=
 a copy from USB to home dir), the connection always becomes terribly slow =
(ping>1000ms), and any other request takes ages to return (thus, if the use=
r uses firefox for example, since it makes quite a lot of disk access to th=
e ".mozilla" directory, its interface freezes until the update if over and =
ping becomes normal again, i.e 60ms)

I managed to optimize this by setting a chunksize of 8kb (smaller seems to =
fail, because my cache is between about 500Mo-2Go, and that makes too many =
files for the cachemanager I think), and by adding an "fs st -allfiles 2000=
0" in afs.conf like this:
afs_server_prefs() { fs storebehind -allfiles 20000 }
It is slighly better with these settings : I still get ping >1000ms, but le=
ss often...

Is there any ways to enhance this again, or should I set some QoS on the sy=
stem to prevent afs daemon to send to many packets at the same time (a solu=
tion that I'd rather avoid, since I'll not have full control over the clien=
t's systems...)?

Tanks a lot for your advices!

Fr=C3=A9d=C3=A9ric.