RE: Advice Required - for avoiding conflict betwen qmail-smtpd, rblsmtpd loaded as shared objects in tcpserver

Hi David.

On Sun, 2 Apr 2017 21:28:47 -0400, David T. Ashley wrote:
> My personal situation is that I had all of these criteria to meet:
> 
> a)Had to be noiseless/fanless -- it would sit in my entertainment center,
> and I wouldn't want it to
> interfere with my video games or Arnold Schwarzenegger movies.
> 
> b)Had to be compact.
> 
> c)Should run a standard Linix distribution--easy to upgrade.
> 
> d)Should support terabytes of storage, if I wish, with no wearout issues.
> 
> e)Should not use much power.  My target was 15 watts -- I'm glad I got a
> solution at 5.5 watts.
> This is under $10 a year -- excellent!
> 
> f)Shouldn't be too expensive.

A-F: CubieBoard2/ExpressoBin seem to satisfy these on their own; both have a SATA connector (the ExpressoBin has the fastest SATA).
Price for a 2GB ExpressoBin version is less than $80; a 1GB version is less than $40.

> g)Should tolerate power loss with no data corruption.
> 
> I looked at industrial computer boards, but these were expensive, and still
> left the UPS issue unaddressed.

CubieBoard2 uses around 500mA at 5V, a connected 2.5" harddisk would use 500mA at 5V too; a total of 1A at 5V = max. 5W if reading/writing to the harddisk all the time.

You can build your own UPS by creating a Y "split" DC-cable, which has two Schottky-diodes embedded (two SR3100 would be fine).
One male DC-plug go into the CubieBoard2.
One female DC-plug connects to a DC power supply.
One female DC-plug connects to a battery.

One diode point from the battery towards the CubieBoard2.
One diode point from the external PSU towards the CubieBoard2.

Eg. the cathodes are connected to eachother.

A simple comparator circuit (with a shunt-regulator) could be used on the primary side of the battery supply (before the step-down converter) in order to monitor how much power is left.

That makes a *very* cheap UPS. :)
I'm running my CubieBoard2 on a $1 DC-DC step-down converter; which can be connected to a string of 12V lead-acid batteries (eg. charged by solar power).

> Finally, I settled on a Lenovo 11e.  You can pick them up at the Lenovo
> outlet store for <$300, easy (just get
> a Windows one so you know it has the bay and hardware for a hard drive).

I actually have a dual-core P4 ThinkCentre (but I don't trust this thing too much and it's drawing way too much power compared to the CubieBoard2).

> The machine is fanless nearly all of the time.  (If I do load the CPU
> heavily, the fan does go on, though, and the power
> consumption can get as high as 15 watts.  But this only occurs when running
> maintenance crons.  HTTP service
> and so on won't do it.)

Not too bad. :)

> The UPS problem is solved automatically, as the laptop's battery acts as a
> UPS.  In fact, I wrote a cron script
> to shut it down if the power is off for too long and the battery's charge
> falls too far:
> 
> http://e3ft.ddns.net/vvcdtapublic/dtapublic/projs/dtats/trunk/projs/20161029
> _server_scripts_automaint_cron/power_fail_shutdown?revision=98&view=markup

Quite uncomplicated. :)

> For the URL above, I will give you one guess about how that is being served
> LOL.

Must be SVN as I expect that noone uses CVS anymore. -I prefer git myself. ;)
My CubieBoard runs multiple kinds of servers too (apache, git, redis, qmail, dovecot, ssh, nfs, netatalk, squid3, ...).

> The approaches you are contemplating are very clever, but for me getting
> essentially a slow PC for 5.5 watts of power consumption works the best.

Your solution isn't too bad either; I did expect a PC to consume more power.
Note: I've also looked into using TV-boxes (the best candidate is the Beelink-GT1 because Armbian supports building debian for it).
Cheap S905 based TV-boxes could also work (if you look [very] carefully on eBay, you might be able to find one supporting Gbit Ethernet for around $30 - please notice that almost all S905 based boxes only support 100Mbit Ethernet, not Gbit Ethernet - but a few KM8 boxes seem to support Gbit Enet).

I think a STM32F4 qmail server would be able to run at milliwatts - perhaps even microwatts. 8)
(the MCU is able to wake up in 4 clock cycles).

Sadly, a git-server really requires a complete Linux installation due to all the tools git is based upon.


Love
Jens