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Date:      Fri, 22 Feb 2013 10:33:47 -0500 (EST)
From:      Rick Macklem <rmacklem@uoguelph.ca>
To:        Daniel Braniss <danny@cs.huji.ac.il>
Cc:        freebsd-stable@freebsd.org
Subject:   Re: zfs/nfs/proftpd problem
Message-ID:  <773493110.3210623.1361547227044.JavaMail.root@erie.cs.uoguelph.ca>
In-Reply-To: <E1U8p9F-0006QB-Dc@kabab.cs.huji.ac.il>

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Daniel Braniss wrote:
> after upgrading the 'ftp storage' from 8.3 to 9.1-stable, our ftp
> server is stuck.
> 
> the old, (ProFTPD Version 1.3.2) and working till before the upgrade
> is stuck
> in nlmrcv:
> ...
> 10000 1213 992 0 44 0 7340 3692 nlmrcv D ?? 0:08.07 proftpd:
> ftp -
> crawl-66-249-73-193.googlebot.com: anonymous/googlebot@google.com:
> RETR 00690145.JPG (proftpd)
> ...
> 
I suspect you know that this is waiting for a reply from some rpc.lockd.

> so we upgraded the ftp server too, to 9.1/ProFTPD Version 1.3.4b and
> this one
> is stuck in rpccwnd:
> 10000 1197 984 0 20 0 32292 4792 rpccwnd D ?? 0:00.01 proftpd: ftp
> -
> mbpro.cs.huji.ac.il: anonymous/mozilla@example.com: LIST (proftpd)
> 
This one is stuck in the client side of UDP for the krpc, in the
primitive congestion control stuff that is there.

> 
> any wise suggestions :-)
> 
Well, maybe not wise, but you may already be aware that NFS etc over
UDP and the NLM are two of my favourite things (especially the NLM).

Basically, it appears to be having difficulties doing RPCs over UDP,
at least for the NLM (rpc.lockd), suggesting some transport related
issue.

First, make sure rpc.statd and rpc.lockd are running on the NFS server
and all clients (or disable use of it via the "nolockd" mount option).

You can also do a "netstat -s" and see if there is a non-zero count
for "fragments dropped due to timeout" in the IP section. (This happens
when your network fabric can't handle the burst of IP fragments
generated by a large RPC message over UDP.)

Things you could try:
- If you are using a udp mount for NFS...
  - reduce your rsize and wsize (especially if "fragments dropped due
    to timeout" is non-zero)
  or
  - switch to TCP

If you are not using udp mounts, then the NLM (rpc.lockd) is using
UDP anyhow. If you don't need multiple NFS clients to see the file
locks, add "nolockd" to your mount(s).

Beyond that, you'll need to capture packets and look at them in
wireshark, to see what is going on.

Good luck with it, rick

> cheers,
> danny
> 
> 
> 
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