Re: Is NFS Locking Reliable?
Our NFS servers for user home directories are on FreeBSD (6.4), MacOSX (10.5), Linux (still 2.4 kernel) and Tru64-UNIX boxes; NFS clients are mostly Linux (2.6 kernel) and FreeBSD (6.4, 7.0, but w/o kernel lockd) systems. I have seen problems with NFS locking even in completely homogeneous environments. With a mix like that, I would not trust it as far as I could throw a Cray :) There are periods of several days without problems, but from time to time, on one, two, or several (but not all) clients application processes which use locking suddenly hang in kernel mode - namely firefox, opera, pine. Lockups are probably the least of your concerns, at least where pine is involved. Dunno what sort of data firefox and opera are protecting from race conditions, but I suppose pine is being used for email. Cases will arise wherein mail mysteriously disappears, because the client and the delivery agent were both updating the inbox at the same time. Often there will be no noticeable symptoms, except for users wondering what happened to that important message they were supposed to have gotten (and which the MTA log shows was in fact delivered). Never export an inbox read/write if reliability of mail delivery is needed. Use IMAP instead. It seems to be no specific operating system problem - all combinations of clients and servers are involved. I suspect the reason NFS locking is so troublesome is that it presents problems which are fundamentally incomputable. Prior to restoration of communication, how can any automaton possibly distinguish between * a temporary loss of the communication link (but the peer is still running and the link will eventually be re-established), and * the peer has crashed, and will eventually reboot? ___ freebsd-questions@freebsd.org mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-questions To unsubscribe, send any mail to freebsd-questions-unsubscr...@freebsd.org
Is NFS Locking Reliable?
I'd like to ask for your experiences with NFS locking in larger environments. Our experiences are not so satisfying. Our NFS servers for user home directories are on FreeBSD (6.4), MacOSX (10.5), Linux (still 2.4 kernel) and Tru64-UNIX boxes; NFS clients are mostly Linux (2.6 kernel) and FreeBSD (6.4, 7.0, but w/o kernel lockd) systems. There are periods of several days without problems, but from time to time, on one, two, or several (but not all) clients application processes which use locking suddenly hang in kernel mode - namely firefox, opera, pine. It seems to be no specific operating system problem - all combinations of clients and servers are involved. There are some suspicious facts that out network may cause problems although not all ip subnets are protected by cisco firewall modules. But there may be other circumstances which could lead to sporadic packet losses or whatever else ... So, if anyone has similar or other experiences with NFS locking, I'm very interested in reading about! Thank you very much in advance! Konrad Heuer GWDG, Am Fassberg, 37077 Goettingen, Germany, kheu...@gwdg.de ___ freebsd-questions@freebsd.org mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-questions To unsubscribe, send any mail to freebsd-questions-unsubscr...@freebsd.org
Re: Is NFS Locking Reliable?
On Tue, 10 Mar 2009, Konrad Heuer wrote: I'd like to ask for your experiences with NFS locking in larger environments. Our experiences are not so satisfying. Our NFS servers for user home This matches my historical experience, especially if you add in periodically wedged and ignored lock state. First, it is useful to realize that locking over NFS has, until version 4, been done outside of NFS itself. That is, there are a pair of daemon (usually called statd and lockd) processes that negotiate the lock outside of the stateless mechanism that is the NFS data access method up to v3. My past v3 experience has been that only in the case where you have exactly the same version of statd and lockd on both sides (on the client and on the server) is it possible that you _may_ experience truly reliable locking. Note that this is only possible with the same OS at the same revision/patch on both client and server. NFS v4 is no longer stateless, and manages locks internally, which I would guess would make things much better, though my experience on mixed environments under v4 is much more limited. What version of the NFS protocol are you using? You can find this out via /usr/sbin/nfsstat If you are stuck with a v3 client, my recommendation would be to turn locking off altogether for that client, as I have found that this works in general better, as the applications desiring the lock are then at least aware that the lock won't work, rather than being led up the garden path by a successful return from a call to lockd that later is not honoured. If upgrading all to v4 is possible, it is probably worth a try, and good luck! Andrew. ___ freebsd-questions@freebsd.org mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-questions To unsubscribe, send any mail to freebsd-questions-unsubscr...@freebsd.org
