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In average the buffers will be filled to 75%.

No suitable buffer allocated

Let's assume there is a request for 200k buffer and lots of 128k buffers allocated, but no buffer larger than 128k allocated in the pool and there is no capacity remaining in the pool. In this case we will take 2 ByteBuffers with 128k and use in ByteBuffersWrapper. 

Pool limit exceeded

Let's assume there is a request for 11Mb buffer and pool limit is 10Mb. In this case we will wait until all buffers return to the pool, take them all, allocate a new HeapByteBuffer for 1Mb and wrap them into ByteBuffersWrapper. When buffers released, we will return only 10Mb buffers to the pool. The new 1Mb buffer will be given to GC.

ByteBuffersWrapper

Wraps several ByteBuffers, extends ByteBuffer.

Writing to disk

We can often see that disk IO operation is the bottleneck in Ignite. So we should try to make writing to disk efficient. 

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What happens if a dump entry doesn't fit into pool size? 

Other ideas

One of the proposed ideas was to switch from writing to several partition-specific files to single dump file. This idea wasn't considered much because of change complexity and limitation for multi-threaded I/O which could be beneficial on some server storages. And it is still possible to achieve sequential writes with multiple partition files.