How to configure UPS to restart servers in the right sequence?

Here we have some servers and almost each of them has a dedicated UPS. There are dependencies between them so they must be switched on in the correct sequence. Ultimately we are experiencing serious problems with the power supply, so the servers are shutdown and then restarted in a random order when power is restored. It is not a problem if the servers were switched off during a blackout, it is important they work correctly without any human intervention once power is restored.

Our UPS are quite cheap and the only configuration parameter useful for my goal is power the load xx seconds after power is restored. In theory putting the right delays on each UPS I can fix the order of server restart but I don't trust the UPS will behave as expected.

Is it the right way to go ?
Do high level UPS give other options to fix the restart sequence ?
One final note: my Ups are in the range of 1000 - 2200 VA

The standard answer for this is "not at all". Fix the software to handle restarts in random order. If you really need SOME servers to start first (example: Active Directory) put them on USV's that are possibly surviving a LOT longer. A low power atom based server is good enough as Active Directory controller and will survive a day on a small USV.

Do high level UPS give other options to fix the restart sequence ?

No. I would say it is generally assumed programmers are competent enough to work around the issue properly.

What you COULD do is:

• Have servers start "randomly". Except for DHCP / Active Directory there is nothing really demanding an order that can not be fixed.
• Have a control server after some time (5 minutes) start the services on the various machines in the correct order.

I would say that this type of setup is a lot more common. I would call any software that REQUIRES server starts in a particular order (outside of pure infrastructure) as broken and unfit for business.

Just as note: our own setup is a low cost 20kva USV (low cost because we got one used) for the servers, with a slaved 2000VA USV for a machine serving as "root" of the network (and backup machine). Slaved means that the USV is behind the big one - so it only switches to battery when the large one (that lasts between half an hour and 8 hours depending on how much of our computing grid is online) is going into terminal shutdown.

Managed Power Distributions Units (rather than the UPS) often do support customised delays in enabling individual outlets after power is resumed.

Typically that is to prevent circuit breakers from tripping when a cabinet full of systems powers up at the same time immediately after power is restored, but that can also be used to preserve the boot order of your system dependancies.

I had this exact issue. The only difference being we invested in sturdy rack mounted APC power units (for example APC SmartUPS 3000 ). With the APC PowerChute network shutdown software (PowerChute Network Shutdown software) , I'm able to shut down and bring up servers in a specific order. Another handy feature of the software was setting the servers to shut down at the very last minute, i.e. calculating how much battery power the APC units had left and shutting down the servers with just enough time for them properly shut down instead of just powering off.

The software is...not user friendly but it's nothing difficult if you take some time to figure it out. If you're interested in investing more in your infrastructure, this is definitely the route to go.