So did anyone else notice how we just plain dropped entirely off the internet a day or two ago? Everything was down. And if that picture isn’t a hint… I had to literally pull the plug for a time period. Why? Listen up.
That server, a Dell PowerEdge, is the main hypervisor for all my websites and associated services. Minus some infrastructure, everything will, at some point take a trip through that device. For me to explain why I upgraded, there’s one more thing I have to explain first. If you already know this, feel free to skip the next section.
What’s A Hypervisor?
I mentioned the word hypervisor up there. A hypervisor, in these terms, is a computer with the dedicated purpose of running virtual machines (VMs). To this end, machines are even given a specialized OS built entirely around managing many VMs in the most efficient manner.
To anyone familiar with VMs, you know that they can take a lot of memory. Well, until this point, this server was equipped with 72 GB of memory. As of now, that’s now 96. It should have been 104 GB, but… Servers must be complicated. Hopefully though… next week it’ll become 120-ish GB.
I did mention that I’m about 8 GB short of where I should have been, right? Yeah, here’s the thing. This server, in particular, has a triple channel configuration for memory. This means that, for example, slots 1, 2, & 3 are grouped together, as well as 4, 5, & 6… see the pattern? Well, Here’s the thing: All channels of a group need to be identical. On top of that, it has two processors (under those giant metal blocks in the middle). Both processors need an identical memory arrangement relative to each other.
Now here’s the problem: The memory upgrade I bought contains 8 sticks of 8 GB (DDR3 ECC dual-ranked 1333MHz for any nerds reading). To properly upgrade memory in this server, you need to change something that’s a multiple of 6. Or more accurately, a multiple of (3 x 2), which… is 6. 8 is not a multiple of 6, and the closest is 6 itself, meaning I had to leave off two entire sticks. Some of you with some math knowledge are probably saying “wait a second… two 8s is 16, yet you’re only 8 short?” Well about that. For a little more detail, all 18 slots in this server were previously filled with 4 GB memory modules. This means that for me to replace one with an 8, I have to remove a 4… meaning a net gain of 4. So, the calculation is not 8 x 2, it’s actually 4 x 2.
Well, this isn’t the end. I mentioned next week, and that’s because four more sticks are on order. These extra four bring my total up to 12, which is divisible by 6, meaning I won’t have unused memory left over.
DO NOTE: This means that I’m going down AGAIN next week to do another memory change!!!