It's so much better than the old UBC memory model. It acts like real swap, however, it's not actually using a swap file. It artificially slows down your container to mimic the behavior of a real server using swap.
Gone are the confusing guaranteed/burst nonsense which leaves so many consumers and even hosts, confused.
Is there any way to disable caching memory inside the container though? Regardless of whether you assign vswap, if you are running the new RHEL6 OpenVZ kernel the containers now use caching memory. Problem it it eats into total amount of memory available on the node.
It's like the swap on a containmer. You've used all your memory, what's left?
+If you have KVM/Xen, you can start to use swap.
+If you have OpenVZ, you have to rely on the host giving you burstable RAM, and it being available. It's in the total RAM.
vswap makes it less confusing as you can have a real server behavior, and because some programs require you to have swap (Oracle), or some will show a red warning (kloxo)
I'm wondering if the memory cache that now shows up in containers is something new or just making visible cache memory that was being used on the Node before. Perhaps just with more granular control of the size at the container level.
There is absolutely no documentation what this change does with respect to cached memory.
My dream is that it works like any other VPS, (VMWare KVM etc)
I just thought that. It's on the OVZ wiki.
They explain vswap on the wiki but not cached memory. I'm assuming it's all inter related somehow but they don't go beyond Vswap explanation. They don't even say how much vswap artifically slows down memory. They just say here it is, eat your gruel and don't ask questions.