TwitterI’ve never used Qmaster before. I’d never gotten around to poking around to see how it worked, and what benefits it might bring. And after the last installation I had on a G5 refused to function under Leopard, I just left well alone.
Qmaster is, quite simply, a way to create a cluster for video rendering. Rendering is just a whole load of number crunching; it’s processor intensive – just squillions of calculations going on to process and render frames of a moving image. If you’ve got multiple processors in your machine, they get used, but on the basis of whenever they’re needed By allocating a cluster, Compressor can allocate these calculations more efficiently, treating each processor as a separate entity.
I like to think of it a bit like counting votes in an election. If you were to put all of the ballot papers in one big pile, and allow the counters to grab whatever they wanted, then go off an count, it wouldn’t be a very efficient use of resources – time would be wasted to-ing and fro-ing, some people might be counting more ballots than others, and there’d probably just be pandemonium and confusion. By allocating everyone ballots to count, and topping them up when they’re done, you save a lot of time and resources are allocated efficiently.
You can also make clusters available to other machines, so that you can allocate rendering tasks across a network, spreading the load and using processors on other machines which might just be sitting idle (I’ve yet to investigate whether you can include multiple machines in a cluster – haven’t delved that far yet).
Creating a cluster turns out to be relatively simple, and is done through System Preferences. Here’s a step-by-step example on how to set your machine up with a cluster for your own use (note I’m using OS X Leopard with Final Cut Studio 2 installed):
1. Open System Preferences.
2. Under “Other”, click on “Apple Qmaster”.
3. The first thing you’ll see is a series of options for “Share this computer as…”. You want to make sure you select “QuickCluster with services”.
4. Next, you’ll see a list of “Services”. Make sure that “Compressor” is checked, and highlighted.
5. Below the list of Services, hit the button labelled “Options for selected service…”. A little sheet will pop out at the top of the window with an option to select “Number of instances”. This is the number of processors you want to assign to the cluster (the language Apple use here isn’t very clear). Ideally, you want to select as many as you can – I have two processors in my machine, so I select “2″. The more processors you make available, the more efficient your cluster will be.
6. Click “OK”.
7. Under “Quickcluster”, you can assign it a name, so that you can easily identify the cluster when it comes to the point of using it.
8. That’s pretty much it. If you click on “Start Sharing” your cluster will spring into life! (sounds more dramatic than it is – it won’t “spring” at all, it’ll just meander in the background, out of sight).
So, now that you have a cluster set up, how do you go about using it? Really simple – assuming you’re familiar with Compressor 3, you just need to do the following:
When you come to submit a job to the queue, by clicking “Submit…”, you get presented with a popup, containing three options: “Name”, “Cluster” and “Priority”. Just select the cluster you’ve just set up and hit “Submit”.
A few things to note:
Using a cluster works best when you have render which will benefit from multi-processing – by that I mean jobs which it will be possible to split to assign to each process of the cluster. For example, rendering a multi-pass DVD file will split the job into several parts and then merge again at the end. Quicktime movies which are reference movies also work well, as there are lots of referenced files which can be assigned to different processes. If all that sounds a little confusing, it’s probably worth doing a little research and reading up on what happens behind the scenes when you render video files.
Also, I’ve yet to toy around with the “unmanaged services on other computers” options – so that might have to be the subject of a future post.