On Fri, 2007-04-20 at 09:04 -0700, Jeremy Chadwick wrote:
> 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).
>
I guess it is possible that the traffic from ftp (or smb) is overloading
the interface; fwiw, if I increase the {recv,send}space to 131072 I can
acheive 32MB+/s using scp (and ftp shows similar values). The real
question is how to avoid these watchdog timeouts during heavy traffic;
the whole point here was to replace windows-based fileshare servers with
FreeBSD for the local network but at the moment it is proving
ineffectual as any samba file transfers stall (much like ftp). I see no
other error messages in the logfiles other than the watchdog timeouts
plus interface down/up messages.
Sven
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