CARP and em0 timeout watchdog

[Jeremy Chadwick]

On Fri, Apr 20, 2007 at 11:51:56AM -0400, Sven Willenberger wrote:
> Having done more diagnostics I have found out it is not CARP related at
> all. It turns out that the same timeouts will happen when ftp'ing to the
> physical address IPs as well. There is also an odd situation here
> depending on which protocol I use. The two boxes are connected to a Dell
> Powerconnect 2616 gig switch with CAT6. If I scp files from the
> 192.168.0.18 to the 192.168.0.19 box I can transfer gigs worth without a
> hiccup (I used dd to create various sized testfiles from 32M to 1G in
> size and just scp testfile* to the other box). On the other hand, if I
> connect to 192.168.0.19 using ftp (either active or passive) where ftp
> is being run through inetd, the interface resets (watchdog) within
> seconds (a few MBs) of traffic. Enabling polling does nothing, nor does
> changing net.inet.tcp.{recv,send}space. Any ideas why I would be seeing
> such behavioral differences between scp and ftp?

You'll get a much higher throughput rate with FTP than you will with
SSH, simply because encryption overhead is quite high (even with the
Blowfish cipher).  With a very fast processor and on a gigE network
you'll probably see 8-9MByte/sec via SSH while 60-70MByte/sec via FTP.
That's the only difference I can think of.

The watchdog resets I can't explain; Jack Vogel should be able to assist
with that.  But it sounds like the resets only happen under very high
throughput conditions (which is why you'd see it with FTP but not SSH).

-- 
| Jeremy Chadwick                                    jdc at parodius.com |
| Parodius Networking                           http://www.parodius.com/ |
| UNIX Systems Administrator                      Mountain View, CA, USA |
| Making life hard for others since 1977.                  PGP: 4BD6C0CB |