[svlug] forwarded message from John Conover

[John Conover]

FYI, I put this in the qmail list this morning. Your opinion may
differ.  They guy is developing a high availability email system for a
medical department. Kind of shows the benifits of Open Software. FYI,
IMHO ...


	John
	
------- start of forwarded message (RFC 934 encapsulation) -------
To: djb-qmail at koobera.math.uic.edu
Subject: Re: Cheap high-availability qmail solution
Date: 20 Nov 1998 19:22:18 -0000

Coda is probably your best bet, since it can be geographically
disperse in case of natural disaster.

Coda running qmail would be a very formidable system. (Use
tcpserver->qmail-pop3 after delivering to ~/Maildir for your secretary
users, virtual domains/smtp/qmtp to local departments for your
sophisticated users.)

If I was the architect, I would probably go with Linux machines. I
would get industrial grade hardware, which carries a 30% cost
premium. Just check that it is manufactured in an ISO9K environment,
and ask their QA department for reliability data. You want 50 year
MTBF, minimum, on all subsystems. This will give you about a 5 year
MTBF on each machine in the distributed architecture-which would push
the overall distributed/replicated system MTBF to well over 50 years.
Rack mount would be good, with hot swappable power supplies with
crowbar over voltage protection. SCSI only, with real IBM or DEC,
(Seagate in a pinch,) HDs (make sure they are manufactured in the IBM
or DEC facility-no OEM stuff,) with no raid. Use a distributed,
replicated file system, like Coda. Geographically disperse,
replicated, is the key issue for you, IMHO. The boxes should be used
only for email, (add other boxes for other things-HW is cheap.)

For the Internet connection to the email distributed system, either
disable inet, running qmail under tcpserver, and named (and only those
two programs,) on the box that connects to the Internet-nothing else,
or the Internet vandals will tear the hell out of your MTBF. No
syslogd, or klogd, etc., (depending on your POV.) Maybe use a Linux
box as a router/firewall in front of each replicated mail
server. Connect the mailserver to the firewall via serial 115 KB,
diald->ppp which goes to slirp in a shell account on the firewall, (or
other such ip masquerading.) Maybe use qmail's UUCP to the Internet
email I/O box.  Such a Linux box would be inexpensive. Well under 500
bucks, (16 meg, 1 gig 486/33 would work fine-but it has to be
industrial strength. A PC 104 from a reputable industrial controller
manufacturer would be fine-as long as the QA department has the
reliability data.)

Develop the Coda/Qmail system-and standardize the configuration, and
transfer everything to a CD, just in case you have to bring the
standard configuration up quick in any of the distributed
machines. Maintain copies of the CD at each geographically disperse
location, with a redundant CD-one on the shelf-the other in the
drive. The CD's should contain enough programs, documentation, etc.,
to light the system to a standard configuration for a new cold
machine. (Verify your CD manufacturer through the QA department-CDs
should carry a hundred year MTBF-mag tape, etc., about a decade, which
could be inadvertently overwritten by a system folk'en or vandal. Not
so with a CD. BTW, tapes have proprietary low level formats-so if you
loose the drive, you loose the tape. The CD formats are international
standards, and will be legacy readable for a long time.)

Operationally, have a daemon ping emails through the geographically
disperse systems every few minutes. The email should have only a
docket number and time stamp, and if the docket number doesn't show up
in the other systems within a reasonable amount of time, the sysadm/SE
should be notified. The ping email should be archived for system
reliability audits.

This is a very inexpensive system for what it does.

        John

BTW, if you want to do this-I notice that you are at a University-and the
EE Department may need a senior project in "real" engineering.

- -- 

John Conover, 631 Lamont Ct., Campbell, CA., 95008, USA.
VOX 408.370.2688, FAX 408.379.9602
conover at inow.com, http://www2.inow.com/~conover/john.html
------- end -------
-- 

John Conover, 631 Lamont Ct., Campbell, CA., 95008, USA.
VOX 408.370.2688, FAX 408.379.9602
conover at inow.com, http://www2.inow.com/~conover/john.html


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