Hello,
sorry for high-jacking this thread, but I have a questing regarding VHD (without
the X): Xen-4.3 switched to upstream QEMUs support for VHD. The dropped their
own VHD implementation in blktap2, which supported backing chains, which QEMU
currently doesn''t. The Xen implementation (xen/tools/blktap2/vhd/lib/
is BSD 3 clause) also supports some kind of journal.
1. Does someone know if the journal support for VHD is somehow related to VHDX?
2. Has somewone put some work into supporting backing chains? I started to have
a look myself some time ago, but had to do other work since then.
Sincerely
Philipp
--
Philipp Hahn Open Source Software Engineer hahn@univention.de
Univention GmbH be open. fon: +49 421 22 232- 0
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On Fri, Nov 01, 2013 at 06:04:19AM +0100, Philipp Hahn wrote:> sorry for high-jacking this thread, but I have a questing regarding VHD (without the X): Xen-4.3 switched to upstream QEMUs support for VHD. The dropped their own VHD implementation in blktap2, which supported backing chains, which QEMU currently doesn''t. The Xen implementation (xen/tools/blktap2/vhd/lib/ is BSD 3 clause) also supports some kind of journal. > 1. Does someone know if the journal support for VHD is somehow related to VHDX? > 2. Has somewone put some work into supporting backing chains? I started to have a look myself some time ago, but had to do other work since then.Hi Philipp, I''m not aware of block/vpc.c (classic VHD) improvements at this time. Out of interest, are the VHD Differencing images you''d like to use come from Xen, VirtualPC, or something else? Stefan
On Fri, Nov 01, 2013 at 06:04:19AM +0100, Philipp Hahn wrote:> Hello, > > sorry for high-jacking this thread, but I have a questing regarding VHD (without the X): Xen-4.3 switched to upstream QEMUs support for VHD. The dropped their own VHD implementation in blktap2, which supported backing chains, which QEMU currently doesn''t. The Xen implementation (xen/tools/blktap2/vhd/lib/ is BSD 3 clause) also supports some kind of journal. > 1. Does someone know if the journal support for VHD is somehow related to VHDX?I don''t believe it is. Despite the similarity in names, VHD and VHDX are completely different formats. I just went and looked at Xen''s libvhd-journal, and per my understanding it is a journal written into a separate file, not related to the actual VHD spec itself. It appears to be used by the VHD utility tools, when updating a VHD image file with operations such as resize, etc.., so they can write a finalized bitmap of all header/metadata changes at once to minimize any potential corruption. Jeff <snipped the rest>