Cool!

Some years ago, we undertook a small experiment with our server room. We had heard that other people were reducing the amount of A/C cooling they used and we wanted to see if it was appropriate for us.

Like a lot of other places, our small server room was kept cool to keep the servers cool; if we were to spend any length of time in there, we would need to put on a jumper or even a fleece to stay warm, as the room was around 10 degrees centigrade. The A/C units were running non stop, and we wanted to see if we could reduce the electric we used.

Essentially, we made a load of measurements to get a base line. These included the core temperature of the UPS, some measurements of the servers and various places within the server room. We were fortunate that our engineering manager had a device that we could borrow for this as he was conducting a number of tests to help the company work towards ISO14001.

He also had a device that allowed us to measure the amount of power drawn by various devices – we seemed to get a couple of slightly odd readings, but when we discounted those, the average values appeared to match what would be expected. We therefore assumed that the errors we had were down to incorrect use.

Having got our base line values, we then started to increase the ambient temperature of the room, and examine what affect this had. Each time, we would leave the changed settings for a couple of weeks to see what would happen; in each case, there was no sign of distress on the servers, so we were able to increase the temperature again.

After some time, we found that the “sweet spot” was between 20 and 24 degrees centigrade. Above 24 degrees, we would see the fans in the servers starting to work much harder and draw more power. Below 20 degrees, the A/C was still running almost all the time. However, in that range, we found that we had the A/C unit running at its least power draw whilst the servers ran at a comfortable level.

We found that in the racks, we had a few “hot spots”; places where the temperature was quite a bit higher than the ambient temperature of the room. We were told that this is normal and generally considered a good thing; these create a thermal current that allows the cooling to happen naturally. The interesting thing was that although the ambient temperature increased by 12 degrees, the hot spots only increased by 3-4 degrees.

Part of the work meant that we had to make sure that the racks were properly positioned in the room to allow for adequate air flow, and the direction of air from the A/C also had to be optimised to prevent “air curtains” forming at various places. We also had to make sure that things such as blanking plates were used to ensure a properly controlled air current within the racks.

Although this all sounds very grand, the room is quite small and most of the work was done in between our normal activities. We were able to make use of some additional advice from the A/C supplier, but that was relatively minor. The total amount of work required was actually quite small, but the results have been very good. We have seen a reduction in power consumption of just under 50% for the server room as a whole – which translates into significant cost savings.

I’ve added a link to a resource that I would recommend to anyone wanting to do work on their server room facilities. It is primarily aimed at North America, but there are some bits that are specifically for the European market. It will take some time to go through all of it, but I consider that it would be time well spent.

http://www.schneider-electric.com/sites/corporate/en/products-services/training/energy-university/energy-university.page?tsk=77518T&pc=26947T&keycode=77518T&promocode=26947T&promo_key=26947T

The really good thing - we now have a server room that we can work in, in reasonable comfort all the time!

Hot, hot, hot...

I booked to take a week off of work last week – no plans to go anywhere, but just wanted a bit of a break. It was a glorious week, with lots of sun, but not too hot, and I managed to catch up on some outstanding jobs at home, such as painting the windows. I also had the chance to sit around and just relax with a glass of wine or two….

So back to work on Monday this week. I thought that I would get an early start as there are a number of projects on the go and I wanted to get a few things out of the way. When I arrived, there was note on the door – the inventory clerk had had problems getting on the system, so had left a note for us to investigate.

When I checked the server room, everything was off and the room was absolutely boiling – we normally run at around 22-24 degrees C as we find that’s a nice temperature to work in, the servers are OK with that and it uses less power to cool the place down. I quickly checked and everything had shut down including the air conditioner which wouldn’t even re-start.

I looked at the UPS and that was showing power going in, but nothing coming out. I looked but couldn’t see a problem so grabbed a couple of power extension leads from our office and ran them around so that we could get a couple of systems running. Priority number 1 was the DHCP / DNS server so that we could get network services and that was the first one running. Next one was email – no problem there, it started up fairly quickly. But with the room so hot, I had to find a way to get some air movement. Even with all the windows and doors open, the room was still close to 40 degrees.

I pinched some fans from the HR office as a quickfix, and after about 20 minutes the maintenance manager came in. He did a quick check on the air con unit and discovered that the power breaker in the mains supply in the factory had tripped out – he reset this, but when the unit started up, it wasn’t cooling anything down. He contacted the service company who sent an engineer down later.

With the rest of my staff in, we started moving a couple of the servers – we have small backup room at the other end of the building so were able to put a couple of them down there as a temporary measure. By about 9:00 am we had most of the system running so that people could get on with the daily work.

When the engineer from the aircon company turned up, he identified that the compressor had failed and needed to be replaced. It took a couple of days to get this, only for him to then discover that anpother part had failed causing all the refridgerant gas to leak out. This is what caused the aircon to fail – and as a result everything over heated.

We checked the UPS settings as it is supposed to send an alert for various events, and it turned out that every event was ticked except the one for temperature. Doh! Basically the device had gone up to 60 degrees C and then just shut everything down. In addition, a switch on the device had tripped preventing any outgoing power.

So now we are almost back to what passes for normal – we have to make time to come in one Saturday to put everything back in place as it takes longer to build a rack up than it does to strip it down. But the aircon is cooling away nicely and hopefully, now we’ve ticked the box, it will warn us of any similar event in future.