Am 09.01.2019 um 17:55 hat Paolo Bonzini geschrieben: > On 09/01/19 17:51, Kevin Wolf wrote: > > Am 09.01.2019 um 17:42 hat Paolo Bonzini geschrieben: > >> On 09/01/19 12:23, Kevin Wolf wrote: > >>> Also note that this is only metadata preallocation; full preallocation > >>> will still return allocated for the protocol layer and so it will always > >>> be slow. > >> > >> Full preallocation these days can create images with preallocated but > >> known-zero blocks, I think? > > > > That would defeat one of the main purposes of preallocation because it > > would still require COW and metadata updates on the first write. > > Sorry I mean at the protocol level, like FALLOC_FL_ZERO_RANGE. It would > still require metadata updates on the filesystem level, unlike "real" > full preallocation, but no qcow2 metadata updates.
preallocation=full doesn't do that. preallocation=falloc is more like it, though that is just posix_fallocate(), not FALLOC_FL_ZERO_RANGE. But when called on a new file, it might result in the same thing? Not sure. Kevin
