I would take it as a simplification to really mean "sequential enough" when writing out the reorganized copy to the long-term storage. With all the different l

I would take it as a simplification to really mean "sequential enough" when writing out the reorganized copy to the long-term storage. With all the different layers in modern storage, I think you can get asymptotically close to the sequential rate once you start hitting some of these other multi-block granularities, i.e. around the block size for flash erasure, encryption, redundancy coding, etc. These don't have to be that big, i.e. several megabytes.