Re: [Qemu-devel] [PATCH] Add qcow2 documentation

[Kevin Wolf]

Am 08.03.2011 14:13, schrieb Stefan Hajnoczi:
> On Tue, Mar 8, 2011 at 11:47 AM, Kevin Wolf <address@hidden> wrote:
>> +         20 - 23:   cluster_bits
>> +                    Number of bits that are used for addressing an offset
>> +                    within a cluster (1 << cluster_bits is the cluster size)
>> +
>> +         24 - 31:   size
>> +                    Virtual disk size in bytes
> 
> Any constraints on these two fields that should be mentioned?

For the size not that I'm aware of.

For cluster_bits qemu restricts it to 512 <= cluster_size <= 2 MB. I
think we should add 512 as a lower limit, anything smaller doesn't make
sense and steals us bits that we want to use for flags.

The 2 MB are more of an implementation limitation. Would you mention it
here? The format shouldn't have any problem with larger sizes.

Kevin