Introduced in Flume 1.5, the Spillable Memory Channel is a channel that acts like a memory channel until it is full. At that point, it acts like a file channel that is configured with a much larger capacity than its memory counterpart but runs at the speed of your disks (which means orders of magnitude slower).

I have mixed feelings about this new channel type. On the surface, it seems like a good idea, but in practice, I can see problems. Specifically, having a variable channel speed that changes depending on how downstream entities in your data pipe behave makes for difficult capacity planning. As a memory channel is used under good conditions, this implies that the data contained in it can be lost. So why would I go through extra trouble to save some of it to the disk? The data is either very important for me to spool it to disk with a file-backed channel, or it's less important...