Write-stream IDs: layering violations

Posted Apr 12, 2015 3:30 UTC (Sun) by giraffedata (guest, #1954)
In reply to: Write-stream IDs by dwmw2
Parent article: Write-stream IDs

Such things are not actually layering violations because of the way they are defined. A command that says, "deallocate this block" is a layering violation. A command that declares, "this block does not back any file" is a layering violation. But a command that says, "Fill this block with zeroes" or even "make this block have unpredictable contents" is not, even if we understand that the device will respond to that information by deallocating the block.

Likewise, declaring that you're going to overwrite two blocks at about the same time in the future does not violate layering. Telling an SSD to put the two blocks in the same erase block would.

What this is instead is messy layering, a form of excessive complexity. That's almost as bad.