Re: [Qemu-devel] Re: [PATCH 2/2] Add flush=off parameter to -drive

[Jamie Lokier]

Paul Brook wrote:
> cache=none:
>   No host caching. Reads and writes both go directly to underlying storage. 
> Useful to avoid double-caching.
> 
> cache=writethrough
>   Reads are cached. Writes go directly to underlying storage.  Useful for 
> broken guests that aren't aware of drive caches.

These are misleading descriptions - because cache=none does not push
writes down to powerfail-safe storage, while cache=writethrough might.

> cache=always (or a more scary name like cache=lie to defend against idiots)
>   Reads and writes are cached. Guest flushes are ignored.  Useful for dumb 
> guests in non-critical environments.

cache=unsafe would tell it like it is.

Even non-idiots could be excused for getting the wrong impression from
cache=always.

-- Jamie