> > 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. > > If so, then this is a serious bug.
.. though it may be a kernel bug rather that a qemu bug, depending on the exact details. Either way, I consider any mode that inhibits host filesystem write cache but not volatile drive cache to be pretty worthless. Either we guaranteed data integrity on completion or we don't. Paul
