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From: mre@beatnix.UUCP (Mike Eisler)
Newsgroups: comp.protocols.nfs
Subject: Re: hard vs. soft mounts on Suns and Pyramids
Message-ID: <2626@elxsi.UUCP>
Date: 1 May 89 23:48:16 GMT
References: <15766@bellcore.bellcore.com> <840@mtxinu.UUCP>
Sender: news@elxsi.UUCP
Reply-To: mre@beatnix.UUCP (Mike Eisler)
Organization: ELXSI Super Computers, San Jose
Lines: 30

In article <840@mtxinu.UUCP> ed@garcia.mtxinu.COM (Ed Gould) writes:
>Hard mounts *are* interruptible with the "intr" option.  That's precisely
>what the option is for, since soft mounts were always interruptible
>in essence.

They are certainly designed and coded to be interruptible in SunOS,
but I know that in at least SunOS 3.2, they didn't work, or they took
a loooong time to interrupt. Can't say about SunOS 4.0 though. In
Lachman's NFS for System V.3, hard mounts were always instantly
interruptible.

>>Further, it says that "filesystems that are mounted `rw' (read-write)
>>should use the `hard' option.  The problem with this is that the entire
>>client and all of its processes can hang when one process is trying to
>>write on a hard-mounted filesystem when the server is down!  This is a
>>terrible situation when the client is a large time-sharing system.

Often, NFS file systems are mounted on a directory immediately under
"/". When a process does a getcwd() this will ultimately result in the
directory entries of "/" being searched and stat()ed. So if one those
directories is a mount point for a NFS filesystem, and the server is
down, getcwd() will hang, and so will the process calling it.  Getcwd()
is called more often than one would think, so most of the interactive
proceses on the client end up hanging. This is particularily noticeable
during login. The fix is to never mount NFS filesystems under a
directory that is likely going to be a component of somebodies cwd, and
"/" is in everyone's cwd. We mount all our NFS filesystems under a
directory called /n.
	-Mike Eisler
	{uunet,sun}!elxsi!mre