On Mon, Jul 16, 2001 at 12:13:10PM -0700, Francois Gouget wrote: | On Mon, 16 Jul 2001, D-Man wrote: | > On Mon, Jul 16, 2001 at 12:45:22PM -0500, Dimitri Maziuk wrote: | > | * D-Man ([EMAIL PROTECTED]) spake thusly: | > | ... | > | > Ok, that makes sense. How about if probability leaves us behind | > | > and a packet is lost? Does NFS provide any way to correct for | > | > that or will your filesystem be hosed? | > | | > | Thankfully, I forget the details[0]. From experience, no, it won't | > | be exactly hosed: you'll end up with a .nfs004950384672385721380937 | > | file that will grow and eventually fill up the partition... nothing | > | an rm -rf / won't fix. And then there's negative cookies and stale | > | mounts that require a reboot on most unices I've seen... | > | > Ok. It sounds like it would still result in data loss :-(. | | Hmm, I'm not an NFS expert but I'll play one on the mailing-list for | you ;-) Please, if there are experts out there, correct me if I'm wrong.
<grin> Everyone's an expert on the internet :-). | AFAIU, NFS has its own mechanism to recover from lost packets. So it | won't be a problem if a packet is lost. Similarly I believe NFS RPCs That's nice to know. | cannot span UDP packets, so there is no chance that a lost packet would | change the meaning of an RPC. The RPC will be lost, pure and simple, and | NFS will have to reissue it or something similar. So I don't think | packet loss is an issue. Good. | What NFS is 'lacking' is congestion control, as in the TCP slow star | and exponential back-off. This means NFS will blast UDP packets as fast | as it cans with no regard for other trafic. This is not really an issue | on a lan and actually had a performance at a time (I think). But if you | go over multiple links, then you may saturate a slower link, causing the | router that is just before it to start dropping packets. Especially if | multiple streams converge there. And once you start dropping packets | performance degrades very significantly. I believe that's why NFS is bad | if there are multiple hops (I get it from a very reliable source that | this is also why it's very bad if the traffic will go over ATM, you need | buffering/traffic shaping). Ok, yeah. I'm not worried about congestion on my home LAN, I was just curios about (theoretical) reliability knowing it used UDP. Thanks for that info! -D