Posts tagged Power Usage

Finally entered the world of Colocation

I’m not entirely sure how long ago I started using dedicated servers (only one for the first few years though) for my sites, but it must be around 10 years or more. My account on is over 10 years old, and in the oldest posts there suggest I had a Cobalt RAQ at the time, while I’m pretty sure that wasn’t the first dedicated server I ever used.

The advantage and disadvantage of dedicated servers is that you’re just renting the hardware. On the one hand this means your host is responsible for any hardware trouble, which can be quite convenient at times. On the other hand, if you need really powerful hardware (high-end CPU, lots of RAM, fast RAID) you’re paying a hefty sum each month for that hardware.

The advantage of colocation is that you can bring your own hardware and the price will typically remain the same (though you might pay more for power usage and rack space for really big and powerful servers). The downside of course is that if anything goes wrong (beyond the scope of “remote hands” from the datacenter at least) you’re responsible for it, which might mean a trip to the datacenter (which will take time, and it may be hard getting replacement parts in the middle of the night or in weekends).

For my first colocated server I’ve settled for a Supermicro 510T-200B case with Supermicro X9SCL-F motherboard as base. For CPU I picked the Intel G620T which is a Sandy Bridge dual-core CPU with roughly the same power as Core2Duo E8400, but with only a 35W TDP. For RAM I just picked cheap 8 GB Kingston ValueRAM and the hard-drives are a cheap OCZ Vertex 2 60 GB SSD for OS and simple 2.5″ 320 GB SATA drive for backups.

The result is a quite small and low-power server which should be fast enough for most purposes. Having said that, the case was a bit tight so next time I’ll probably spend a little more on the case and get a Supermicro 813MT-350CB instead, which also has space for four normal 3.5″ drives and uses rails instead of cage nuts.

The server is colocated (as of Wednesday August 24) at Serverius, who had a very good deal on WHT: 1U, 25TB and 1 ampere power (my server will use only about 25% of that) for 39 euro per month (excl. VAT). They are clearly overselling on bandwidth with this deal, but I don’t mind as I don’t really need that much anyway.

Now for the embarrassing part: when I showed up I seemed I had forgotten to take with me just about everything except the server itself. Serverius normally requires customers to bring their own power cable, CAT cable and cage nuts (for which you also need a screwdriver) and I didn’t bring any of that. Well I did bring a power cable, but the wrong one: the required the extension cable kind, not power cables with a normal plug.

But fortunately they were courteous enough to lend me all that. And while they seem very boringly simple cage nuts are actually quite expensive, which has to do with the requirements they have to operate at or something. Anyway I just have to remember to bring my own (to replace what I borrowed) next time 🙂

Although the spot they allocated me in the rack was quite hard to get to (near the top of the rack, just below their speedtest server) I was able to install the server without to much trouble. The real problem was getting IPMI to work. But for more on that, see my next post.

At this time I’ll see how things go for a few weeks and if everything goes as well as I hope it will, I’ll probably start colocating most of my servers, possibly even in a private half rack. The only ones I might keep renting are those that need loads of bandwidth, as it is still simply cheaper to rent those at providers who oversell their bandwidth (or otherwise can get better bandwidth deals than that would be possible with colocation).

How to calculate kWh (kilowatt-hour)

A colocation provider I am interested in quotes €0.15 per “kWh” for power usage. They also mentioned “1 ampere equals about 166 kWh”. I wondered how they calculated these numbers and how I can calculate power usage in kWh myself.

The first thing you might want (or need) to calculate is how much Watt (W) or Ampere (A) a device (like a server) uses. Power usage can greatly depend on the components used and the load on the server (idle or full). The simple formulas are as follows:

Watt = Volt * Ampere
Ampere = Watt / Volt

So if you have a device that uses 1 Ampere at 230 Volt (default voltage in the Netherlands) then it’ll use 230 Watt. Per hour it will use 230 Watt-hour (Wh).

The k in kWh refers to “kilo” or 1000, so 230 Wh equals 0.23 kWh. And 166 kWh (see quote in first paragraph) is actually 166000 Wh. But where did they get that figure? The answer is that they calculate power usage per month. There are 720 hours in a 30 day month (24 hours * 30 days). So their calculation was (rounded up):

1 Ampere * 230 Volt * 24 hours * 30 days = 166 kWh per month

Anyway, so to calculate the monthly kilowatt-hour (kWh) usage of a device (assuming you already know how much Watt it uses; this can be easily found out using a Wattmeter) the formula is:

kWh per month = Watt * 24 hours * 30 days
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