(1) Varnish exists, so we can actually run it and analyze its performance. There's no need for "this can't work because X" arguments because we know whether it can work or not.
The author claims Varnish works with huge mappings too. In another article: "For example, Varnish does not ignore the fact that memory is virtual; it actively exploits it. A 300-GB backing store, memory mapped on a machine with no more than 16 GB of RAM, is quite typical."
(2) Varnish doesn't ignore the fact disk is slower than RAM. Its data structures are built to minimize page faults, and thus seeks, for this reason. See also: http://queue.acm.org/detail.cfm?id=1814327
The virtual memory abstraction leaks, just like every other abstraction. That doesn't make it worthless.
(3) Files aren't append-only: you can reuse space for a different purpose when you don't need it for its original purpose anymore. How do you think databases work? Or filesystems?
(4) The author's not talking about using disk-backed memory for your general purpose heap. He's talking about using the virtual memory system to access a giant cache on disk.
So is the author wrong about everything? Varnish seems to work, so if he's wrong he's getting away with it.
The author claims Varnish works with huge mappings too. In another article: "For example, Varnish does not ignore the fact that memory is virtual; it actively exploits it. A 300-GB backing store, memory mapped on a machine with no more than 16 GB of RAM, is quite typical."
(2) Varnish doesn't ignore the fact disk is slower than RAM. Its data structures are built to minimize page faults, and thus seeks, for this reason. See also: http://queue.acm.org/detail.cfm?id=1814327
The virtual memory abstraction leaks, just like every other abstraction. That doesn't make it worthless.
(3) Files aren't append-only: you can reuse space for a different purpose when you don't need it for its original purpose anymore. How do you think databases work? Or filesystems?
(4) The author's not talking about using disk-backed memory for your general purpose heap. He's talking about using the virtual memory system to access a giant cache on disk.
So is the author wrong about everything? Varnish seems to work, so if he's wrong he's getting away with it.