Can multiple Colab notebooks share the same Runtime?

Question

In Q1 2019, I ran some experiments and I noticed that Colab notebooks with the same Runtime type (None/GPU/TPU) would always share the same Runtime (i.e., the same VM). For example, I could write a file to disk in one Colab notebook and read it in another Colab notebook, as long as both notebooks had the same Runtime type.

However, I tried again today (October 2019) and it now seems that each Colab notebook gets its own dedicated Runtime.

My questions are:

When did this change happen? Was this change announced anywhere?
Is this always true now? Will Runtimes sometimes be shared and sometimes not?
What is the recommended way to communicate between two Colab notebooks? I'm guessing Google Drive?

Thanks

user_8841057 · Answer

Distinct notebooks are indeed isolated from one another. Isolation isn't configurable.

For file sharing, I think you're right that Drive is the best bet as described in the docs: https://colab.research.google.com/notebooks/io.ipynb#scrollTo=u22w3BFiOveA

user_15532649 · Answer

I have found no easy way of running multiple notebooks within the same runtime. That being said, I have no idea how this effects the quota. On my real computer, I'd limit GPU memory per script and run multiple python threads. They don't let you do this, and I think if you do not use the whole amount of RAM, they should not treat that the same as if you had used all of that GPU for 12 or 24 hrs. They can pool your tasks with other users.

Can multiple Colab notebooks share the same Runtime?

2 Answers