Date: Tue, 08 Jan 2013 10:22:16 -0500 From: Jason Keltz <jas@cse.yorku.ca> To: Andrey Simonenko <simon@comsys.ntu-kpi.kiev.ua> Cc: FreeBSD Filesystems <freebsd-fs@freebsd.org> Subject: Re: Problems Re-Starting mountd Message-ID: <50EC39A8.3070108@cse.yorku.ca> In-Reply-To: <20130108150508.GA2248@pm513-1.comsys.ntu-kpi.kiev.ua> References: <CAG27QgRi89jHWeqzuNikpGM7=JiV%2BDB8f5Xu0JYGhEfQwOrjKQ@mail.gmail.com> <20130103123730.GA19137@pm513-1.comsys.ntu-kpi.kiev.ua> <CAG27QgTuGyPSVxTbCnP3U494ftPxzX5HD56Mtkc-2jMFPNk=ZQ@mail.gmail.com> <20130108150508.GA2248@pm513-1.comsys.ntu-kpi.kiev.ua>
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On 01/08/2013 10:05 AM, Andrey Simonenko wrote: > I created 2000 file systems on ZFS file system backed by vnode md(4) > device. The /etc/exports file contains 4000 entries like your example. > > On 9.1-STABLE mountd spends ~70 seconds in flushing current NFS exports > in the NFS server, parsing data from /etc/exports and loading parsed > data into the NFS server. ~70 seconds is not several minutes. Most of > time mountd spends in nmount() system call in "zio->io_cv" lock. > > Can you show the output of "truss -fc -o /tmp/output.txt mountd" > (wait wchan "select" state of mountd and terminate it by a signal). > If everything is correct you should see N statfs() calls, N+M nmount() > calls and something*N lstat() calls, where N is the number of /etc/exports > lines, M is the number of mounted file systems. Number of lstat() calls > depends on number of components in pathnames. Andrey, Would that still be an ~70 second period in which new mounts would not be allowed? In the system I'm preparing, I'll have at least 4000 entries in /etc/exports, probably even more, so I know I'll be dealing with the same issue that Tim is dealing with when I get there. However, I don't see how to avoid the issue ... If I want new users to be able to login shortly after their account is created, and each user has a ZFS filesystem as a home directory, then at least at some interval, after adding a user to the system, I need to update the exports file on the file server, and re-export everything. Yet, even a >1 minute delay where users who are logging in won't get their home directory mounted on the system they are logging into - well, that's not so good... accounts can be added all the time and this would create random chaos. Isn't there some way to make it so that when you re-export everything, the existing exports are still served until the new exports are ready? Would this be the same for NFSv3 versus NFSv4? I suspect yes. Jason.
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