There is no single way to control the memory usage using system tools except maintaining mongod instances on dedicated virtual machines without running further services. There are numerous complaints from people about this stupid architectural decision from various side and 10gen is doing nothing to change this brain-dead memory model.
Can someone explain to me why this is actually a big issue? Except for really tiny apps, I imagine that having dedicated VMs for your MongoDB actually would be perfectly fine? Probably even preferred?
I was wondering the same. It's pretty standard for databases to not be very good about sharing with others, memory-wise. That's why having a dedicated server is such a popular best practice for non-puny applications. And MongoDB says it's not designed for puny applications right there in its name.
There are fairly straight-forward ways to control memory usage in MongoDB, especially if this is a concern for you. All you need is a bit of OS know-how and it works just fine.
We run both large (multi-shard clusters) and small memory (500MB - 2GB) use instances of MongoDB and have no problems.
It would be good to have developers acknowledge that, perhaps, they may not have all the information instead of declaring that something can't be done.
Either jason has something really interesting up his sleeve or he simply doesn't know what he's talking about.
Last I checked linux had no interfaces to partition the pagecache in a meaningful way, short of rather extreme gymnastics involving kernel-patches or tmpfs abuse.
If that has changed then I'd certainly also be curious to hear about it.
Pretty much any sane architecture has machines dedicated to handling the data store (MySQL, Mongo or whatever). If you are scaling up from a single machine, this is the first split you make.
Can someone explain to me why this is actually a big issue? Except for really tiny apps, I imagine that having dedicated VMs for your MongoDB actually would be perfectly fine? Probably even preferred?