Battery backups: maintaining access when there’s no power

A little background: Some years back I learned a very hard lesson about losing power on a RAID array that didn’t have an onboard battery backup. The result was ~7TB of data gone, about 1.5TB completely irreplaceable including old school work and photos. This was a hard pill to swallow and helped me get better about redundant backups and another thing that was especially important: UPS backups, or Uninterruptible Power Supplies.

A UPS is a device which provides power for a short time during a home or business power failure by providing an AC output to whatever is plugged into it. I have several of these scattered throughout my home, including for my desktop and a couple lights around the house which act as emergency lighting using older, smaller UPS devices. My servers are always running UPS backups, but on a big larger scale.

My company was kind enough in the fall of last year to be giving away a large amount of hardware. In this was a 2U style UPS system which can run all of my (4) 2U servers, firewall and backbone switches in my basement for about 30-40 minutes. I also, however, had my old UPS backups: a 1350VA and 1500VA systems. Now, I wanted to use these to their maximum potential.

I had to move around the server rack (store bought metal shelving FTW) and it gave me a great opportunity to plan ahead for what I wanted to do. Most servers come with redundant power supplies; That is, they allow multiple inputs, so if one power supply fails or is no longer providing/receiving power, the server will switch to the other without interruption or power loss. Neat, eh?

I ran all the primary power supplies into the new UPS backup and then routed all my secondary power supplies and networking hardware into the older UPS units. This allows a total runtime somewhere in the 40+ minute range during a power outage. Not bad, but there’s a catch: How do I shut down (2) ESXI hosts, (2) unRAID hosts and multiple other smaller systems when the power is out and I need remote access? Simple: Battery backup on my desktop in my office.

I used yet another UPS unit in my office and ran a dedicated 10GB SFP line to my core switch in the basement which is also on a UPS. This allows my desktop to run somewhere between 25-30 minutes off power along with some LEDs in my office acting as emergency lights essentially, and one large monitor. I’ve done testing but I finally had a real situation pop up.

Last night we had quite a wind storm and the power was out for about 30 minutes or so. Sometimes my power flashes for 1-2 minutes but this was a long outage it seemed. After ten minutes, I logged in and began gracefully shutting down the VMs on the ESXI hosts and shut down my two unRAID hosts as well. In just a few minutes, my entire network was gracefully shutdown, without data loss or interruption. Adding to this, I was actually in the middle of a hard drive swap on one of my unRAID hosts which was done without issue due to the UPS backups. Another win for preparedness.

I hope this gives you, the reader, some ideas for a home network or a small business and shows why this is so important; Had I had a complete power failure without the battery backups, I could risk losing multiple 10’s of terabytes of data and could have corrupted the disk rebuild on my unRAID system. A little planning goes a long way in this case. Plus, it’s just cool; Why else would we homelab? Cheers!

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