Re: [Qemu-devel] [PATCH v3 1/3] qcow2: Document some maximum size constraints

[Alberto Garcia]

On Wed 14 Nov 2018 12:03:17 AM CET, Eric Blake wrote:
> @@ -427,7 +451,9 @@ Standard Cluster Descriptor:
>  Compressed Clusters Descriptor (x = 62 - (cluster_bits - 8)):
>
>      Bit  0 - x-1:   Host cluster offset. This is usually _not_ aligned to a
> -                    cluster or sector boundary!
> +                    cluster or sector boundary!  If cluster_bits is
> +                    small enough that this field includes bits beyond
> +                    55, those upper bits must be set to 0.

While I think that it's good to have a 56 bits upper limit for both
compressed and uncompressed clusters, I'm wondering: is it theoretically
possible to have data clusters above 64PB if they're all compressed?

Berto