8.0 network problem

[Matthew Seaman]

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On 05/07/2010 01:52:11, David Warren wrote:
>      I've got a persistent problem with my LAN.  I'm running a FreeBSD 8.0
> box as a home server performing the following functions for wired and
> wireless networks: router; firewall; DHCP server; and file server.  For what
> it's worth, I've got ZFS up and running as the main filesystem.  The
> recurring issue is that file transfers from the FreeBSD box to computers on
> the wired network (gigabit) start out fast and then become agonizingly
> slow.  I'm sharing home directories over Samba, and those transfers work
> briefly and then tail off to a few kilobytes per second.  The failure is
> somewhat predicatable in that it tends to happen once a few hundred
> megabytes have been transferred.  I've swapped out hardware, I've Googled
> extensively, and all of the (possibly benign) error messages that I've found
> have been eliminated.  I'm happy to post logs, configs, etc., and I'd
> appreciate any help with a diagnosis.  For the moment:

Does this affect both wired and wireless LANs?  Does this affect
specific protocols more severely than other protocols?  Does this affect
all traffic happening at that point, all traffic on a particular
interface or just specific connections?

The effect you describe sounds bizarrely like entropy-pool exhaustion,
which would kill any traffic over your wireless network, or anything
using crypto protocols on either wired or wireless nets.  I say "sounds
like" because the yarrow entropy pool maintenance code in FreeBSD is
extremely good, and I've seen FreeBSD boxes serving HTTPS at Mb/s
without anything like what you are experiencing.  Also, you're seeing it
affect Samba over a wired connection, and that should be minimally
affected by that sort of thing.  Hmmm...

Can you try transferring some large files (DVD .iso images around a few
GB in size are handy for this) between systems using:

     * netcat or HTTP over wired connection
     * ssh over wired connection
     * netcat or HTTP over wireless
     * ssh over wireless

Try these in both directions -- this should help show if it's slow disk
performance on the receiving side.

Also, check the output of 'netstat -i' to see if interface error
counters are increasing: Ierrors, Idrop and Oerrors should all ideally
be zero.  If you see those starting to rise, it means either there's a
configuration problem somewhere, like a duplex mismatch [no evidence for
that from the ifconfig output you showed though] or perhaps there's
still some dodgy hardware somewhere on your network despite all the
swapping-out you've been doing.

One final thought -- perhaps this isn't to do with the network at all,
but it's disk IO performance bottoming out.  In which case you should be
able to see much the same effect copying files between different zpools,
or between your main zpool and say, a USB memory stick.

	Cheers,

	Matthew

- -- 
Dr Matthew J Seaman MA, D.Phil.                   7 Priory Courtyard
                                                  Flat 3
PGP: http://www.infracaninophile.co.uk/pgpkey     Ramsgate
JID: matthew at infracaninophile.co.uk               Kent, CT11 9PW
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