Status Update: ESX Server Sparse Extent
The ESX Server Sparse Extent has the same magic number and very similar header
fields, with the existing VMDK3Header
. Most code can be reused to add support
for this format. Only a few fields are extra to VMDK3Header
, they are used to
save the extent name/description and detect the unclean shutdown.
The COWDHeader structure is like:
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So, only tiny changes are needed to handle this header. Now what we need is to collect real world images to test its support.
PS: There’s another important extent type: vmfs. Currently there’s no open specification for it. There’s an open sourcey driver: [http://code.google.com/p/vmfs/][] The driver can do nothing to write to vmfs, because it is implemented by reverse engineering vmfs files. This factor makes adding this format to our driver a hard job.