Multiple serial consoles via null modem cable

[Jeremy Chadwick]

On Tue, Jan 12, 2010 at 02:50:29PM -0500, Charles Sprickman wrote:
> On Tue, 12 Jan 2010, Charles Sprickman wrote:
> 
> >On Jan 12, 2010, at 12:04 PM, Boris Samorodov <bsam at ipt.ru> wrote:
> >
> >>On Tue, 12 Jan 2010 17:14:44 +0200 Marin Atanasov wrote:
> >>
> >>>I'm thinking about the following situation - 1 system acting like a host
> >>>with a serial port hub, each port of the hub is connected to a different
> >>>machine on sio0, using null modem cables.
> >>
> >>Along with milti-io serial cards we use multi-usb serial
> >>converters, such as SUNIX UTS7009P (7 USB to serial adapter):
> >>http://www.sunix.com.tw/it/en/LinkCraft/UTS4009P_UTS7009P.htm
> >>
> >
> >I need to look it up when I'm in front of a real computer, but
> >there are a number of reasonably priced multport USB to serial
> >converters out there.
> 
> Here we go:
> 
> http://www.usbgear.com/USB-Serial.html
> 
> Some very cool stuff there.  They also list the chipset used in some
> of those so you have some idea if it will work with FreeBSD.  I
> think Vixie originally pointed me to this model:
> 
> http://www.usbgear.com/computer_cable_details.cfm?sku=USB-16COM-RM&cats=199&catid=493%2C494%2C474%2C199%2C461%2C106%2C1009%2C601
> 
> If anyone has the lowdown on which chipsets generally work with
> FreeBSD (especially with all the changes in 8.0), that would be
> great.

The same device appears here:

http://www.serialgear.com/USB-16COM-RM.html
http://www.allserial.com/usb_16com-rm.html

Quite inexpensive compared to an actual serial console server!  I had no
idea such a device existed (well, USB-to-serial adapters, sure, just not
ones which housed 16 adapters or was rack-mountable.  :-) ).  Decently
sized FIFO buffers as well (128/384 byte Tx/Rx), at least compared to a
classic 16650A (14/16 byte Tx/Rx).  Usually larger FIFO == can handle
higher bps without character loss.

I've 5 questions about this device:

* Does it work with/use hardware flow control (CTS/RTS)?
* Have you tested it for character loss at 115200bps rates?
* How do you configure each port (speed, flow, etc.)?
* Does it work under FreeBSD 8.x (given that the entire USB stack
  was re-written)?
* Do you have any idea what the power usage is on this device (in amps)?
  (Our MRV claims 1A max, but drives about 0.25A or so).

> The above model works great on an old 4.11 box.  It's an FTDI
> chipset - at the very bottom of the page they even claim FreeBSD and
> OpenBSD support.
> 
> dmesg:
> 
> uhub2: Genesys Logic USB Hub, class 9/0, rev 1.01/0.11, addr 2
> uhub2: 7 ports with 7 removable, self powered
> ucom0: FTDI USB FAST SERIAL ADAPTER, rev 2.00/5.00, addr 3
> [...]
> ucom11: FTDI USB FAST SERIAL ADAPTER, rev 2.00/5.00, addr 8
> [...]
> uhub3: Genesys Logic USB Hub, class 9/0, rev 1.01/0.12, addr 9
> uhub3: 4 ports with 4 removable, self powered
> ucom12: FTDI USB FAST SERIAL ADAPTER, rev 2.00/5.00, addr 10
> [...]
> ucom15: FTDI USB FAST SERIAL ADAPTER, rev 2.00/5.00, addr 11

Very nice -- the fact they're using FTDI chips is good (from what I
understand of USB-to-serial adapters).

> > We have a 16 port model that's rack mounted and cost around $400.
> >It works better many of the more expensive multiport serial cards.
> >Paired with conserver, it's a really nice solution.  Conserver's
> >logging is great...
> >
> >I've used old dedicated terminal servers in the past and they can
> >be a pain to deal with.  The newer ones are probably nicer, but
> >are also lots of money.

Classic devices (like the Portmaster) are indeed a pain in the butt to
deal with.  I've no experience with Ciscos, but in the case of the PM,
documentation vs. implementation mismatch galore.  The MRV devices are
thoroughly documented (it borders on overwhelming -- I'd say half of the
configuration parameters are foreign to me), and I think the Cyclades TS
devices are as well; it's the cost of the Cyclades which blows my mind
(zero justification for it too, other than "enterprise cost mentality",
e.g. charge as much as possible because large businesses will pay it).

I think for folks who want a multiport serial console device that sits
on Ethernet, the MRV or Cyclades device would be a good choice, since
it's a standalone unit which doesn't need to be physically cabled to a
"host" box (and often a good choice for those who want modem-based OOB
access to devices, since it can house a v.90 modem).  For those with
less requirements and want to spend less, the above USB-to-serial device
looks fantastic -- and at almost 1/4th the cost of our MRV.  :-)

As usual, thanks for the insights, Charles!

-- 
| 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 |