On Fri 28 Jun 2019 11:20:57 AM CEST, Kevin Wolf wrote: >> >> I would consider 64k cluster/8k subcluster as too extreme for me. >> >> I forgot to add: this 64k/8k ratio is only with my current prototype. >> >> In practice if we go with the 128-bit L2 entries we would have 64 >> subclusters per cluster, or 32 if we want to have a separate >> QCOW_OFLAG_ZERO for each subcluster (would we need this?). > > Yes, I think we'd want to have a separate zero flag for each > subcluster. Otherwise, when writing to a zero cluster, you'd have to > COW the whole supercluster again.
Yes if the original cluster had the QCOW_OFLAG_ZERO bit, not if it was simply unallocated. Berto
