> Let me just emphasize what Stephen is pointing out: if requests are
> properly merged at higher layers, then merging is neither required nor
> desired. [...]
this is just so incorrect that it's not funny anymore.
- higher levels just do not have the kind of knowledge lower levels have.
- merging decisions are often not even *deterministic*.
- higher levels do not have the kind of state to eg. merge requests done
by different users. The only chance for merging is often the lowest
level, where we already know what disk, which sector.
- merging is not even *required* for some devices - and chances are high
that we'll get away from this inefficient and unreliable 'rotating array
of disks' business of storing bulk data in this century. (solid state
disks, holographic storage, whatever.)
i'm truly shocked that you and Stephen are both saying this.
Ingo
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