Tag Archives: Building cluster

Building a small CPU/GPU cluster – day 1

I somehow was given the responsibility over a small mixed CPU/ GPU cluster and have the questionable honour of installing it. Since I have limited experience in this, I decided I will document it in an online form, such that I can come back to my notes in the future, should something break. WARNING: I am no expert at all in cluster administration/installation or the like, anything stated here may well be completely silly or wrong. I take no responsibility for that. 

Here is a vague picture of what the cluster will look like when finished.


The headnode is setup with a MegaRAID SAS 9260-8i RAID controller and 8 2 TB harddrives. Since on day one all I did was configure the RAID settings, I will give a summary of the RAID setup I did today.

First things first, what RAID level should I use?

Ideally I want RAID level 1 on two drives that make up my root partition later in the installation and RAID 6 on my /home partition. Ideally I want two harddrives to be dedicated to root and the rest to /home. However, since I only have 2 TB drives and I really don’t need a 2 TB root partition I decided to not go with this setup, but instead have everything setup using RAID level 6 with two virtual devices (vd0 will eventually be /) and (vd1 will eventually be /home).

To be honest I had very little idea about RAID levels or anything connected to physical/ virtual devices but the user guide for the MegaRAID controller was very useful in helping with certain decisions. Therefore I will link to it here. I have also taken a couple of images out of it for illustration purposes here.

The nice thing about this RAID controller is the very user friendly webbios interface. Therefore I power the headnode on and enter the webbios by pressing ctrl+h on boot-up. Soon a welcome screen greets me and I click on the configuration wizard link to get to this:


In my case I then clicked on chose New configuration, since I will start from scratch, but am working on a system with some previous configurations. I will then also choose a manual setup of, so that I can configure my virtual devices exactly how I want them. Now I just walk through the configuration wizard:

  1. When I ended up on a screen like this:
    I selected all the physical drives on the left (using shift) and then clicked on ‘add to array’.
  2. Once all the drives were added and I was happy with the drive group, I clicked on ‘accept DG’ on the right and then next.
  3. Now I am in the virtual drive configuration window of my drive group 0 (and only drive group).
    At the moment there is one virtual drive. I click on it and configure it the way I like:
    – RAID 6
    – Strip size: 128 kB- Access policy: Read + Write
    – Read Policy: Normal
    – Write policy: WThru
    – I/O policy: direct
    – Disc cache policy: disabled
    – Disabled BGI: no
    and set the drive size to 50 GB (for root). I accept the settings and then create a second virtual drive with identical settings but now use the left over drive size, which is around 10.8 TB on the chosen RAID6 in my system.
  4. Once I am happy with my virtual devices I accept their configuration.
  5. When I am prompted to save the new configurations I do so.

Now I have my RAID setup in the way I want. The welcome screen should now show me two virtual drives and 8 physical drives and give me a ‘pretty’ graphic about how everything is set up.  What happens next is that the background initialisation check will start running and I just let ot. This will take a while (I have projected something like at least 24h on my setup) and since I have some other things to do anyway, I let the initialisation happily check away, until my next free time-slot for some more cluster building.