NFS async writes - HEADSUP

Matthew Dillon dillon at
Sat Jul 18 15:22:17 PDT 2009

    Heads up folks.  DragonFly NFS clients in master can now do async
    writes and when the kernel flushes we're talking 64 16K packets at
    least.  On a fast GigE ethernet this can blow out the NFS server's
    socket buffer (if the server isn't running the latest DragonFly master).

    If such a situation arises for you, either use a TCP NFS mount instead
    of UDP (-T option to mount_nfs, or "tcp" option in /etc/fstab), or
    reduce the maxasyncbio's with a newly available sysctl called
    vfs.nfs.maxasyncbio.  The default is 64, which requires about 2MBytes
    of sockbuf space on the NFS server.

    Again, look forward to a bit of instability with NFS on the master
    branch for the next few days as the kinks get worked out.

					Matthew Dillon 
					<dillon at>

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