Date: Mon, 22 Dec 2014 10:04:48 -0500 From: John Baldwin <jhb@freebsd.org> To: freebsd-stable@freebsd.org Subject: Re: NFS negative name caching and amd Message-ID: <201412221004.48504.jhb@freebsd.org> In-Reply-To: <20141221102746.GA11278@odi.ci.com.au> References: <20141221102746.GA11278@odi.ci.com.au>
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On Sunday, December 21, 2014 5:27:46 am Richard Perini wrote: > > We're struggling with an NFS negative name caching issue that results in > a file created by an NFS client 'A' being invisible on client 'B' for up > to client A's negnametimeo value. In our scenario, a process on client > A creates a file, and passes a message to another process which may > run on client B. The second process expects the file created by A to > be available. Which NFS server are you using? If it is a FreeBSD NFS server, try changing vfs.timestamp_precision to 2 (or 3) and seeing if that reduces the amount of time you have to wait until the directory's ac timeout. Another possible the fix is to be careful to not open the file until you know it exists if you still want to keep the reduced LOOKUP RPC load from caching negative lookups. > We're running a mix of 9-stable and 10-stable machines, and the problem is > common to both. > > The obvious fix is to set the nfs mount option 'negnametimeo' to 0, but > unfortunately we also have 'amd' in the picture (which we also need in our > environment). Amd doesn't understand negnametimeo and ignores it, leaving > it set to the system default of 60 seconds (as shown by nfsstat -m). Have you tried autofs for 10-stable? Is it able to pass this option to NFS if you use it? If that works, I would prefer that to be the long term solution for this. I'm not a huge fan of adding kernel options to override each NFS default mount option if we can help it. -- John Baldwin
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