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Re: [Qemu-devel] [question] is it posssible that big-endian l1 table off
From: |
Eric Blake |
Subject: |
Re: [Qemu-devel] [question] is it posssible that big-endian l1 table offset referenced by other I/O while updating l1 table offset in qcow2_update_snapshot_refcount? |
Date: |
Thu, 09 Oct 2014 08:58:14 -0600 |
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Mozilla/5.0 (X11; Linux x86_64; rv:31.0) Gecko/20100101 Thunderbird/31.1.1 |
On 10/09/2014 05:17 AM, Zhang Haoyu wrote:
> Hi,
> I encounter a problem that after deleting snaptshot, the qcow2 image size is
> very larger than that it should be displayed by ls command,
> but the virtual disk size is okay via qemu-img info.
> I suspect that during updating l1 table offset, other I/O job reference the
> big-endian l1 table offset (very large value), so the file is truncated to
> very large.
Not quite. Rather, all the data that the snapshot used to occupy is
still consuming holes in the file; the maximum offset of the file is
still unchanged, even if the file is no longer using as many referenced
clusters. Recent changes have gone in to sparsify the file when
possible (punching holes if your kernel and file system is new enough to
support that), so that it is not consuming the amount of disk space that
a mere ls reports. But if what you are asking for is a way to compact
the file back down, then you'll need to submit a patch. The idea of
having an online defragmenter for qcow2 files has been kicked around
before, but it is complex enough that no one has attempted a patch yet.
--
Eric Blake eblake redhat com +1-919-301-3266
Libvirt virtualization library http://libvirt.org
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- [Qemu-devel] [question] is it posssible that big-endian l1 table offset referenced by other I/O while updating l1 table offset in qcow2_update_snapshot_refcount?, Zhang Haoyu, 2014/10/09
- Re: [Qemu-devel] [question] is it posssible that big-endian l1 table offset referenced by other I/O while updating l1 table offset in qcow2_update_snapshot_refcount?,
Eric Blake <=
- Re: [Qemu-devel] [question] is it possible that big-endian l1 table offset referenced by other I/O while updating l1 table offset in qcow2_update_snapshot_refcount?, Zhang Haoyu, 2014/10/09
- Re: [Qemu-devel] [question] is it possible that big-endian l1 table offset referenced by other I/O while updating l1 table offset in qcow2_update_snapshot_refcount?, Max Reitz, 2014/10/12
- Re: [Qemu-devel] [question] is it possible that big-endian l1 tableoffset referenced by other I/O while updating l1 table offset in qcow2_update_snapshot_refcount?, Zhang Haoyu, 2014/10/12
- Re: [Qemu-devel] [question] is it possible that big-endian l1 tableoffset referenced by other I/O while updating l1 table offset in qcow2_update_snapshot_refcount?, Max Reitz, 2014/10/13
- Re: [Qemu-devel] [question] is it possible that big-endian l1 tableoffsetreferenced by other I/O while updating l1 table offset in qcow2_update_snapshot_refcount?, Zhang Haoyu, 2014/10/13
- Re: [Qemu-devel] [question] is it possible that big-endian l1 tableoffsetreferenced by other I/O while updating l1 table offset in qcow2_update_snapshot_refcount?, Max Reitz, 2014/10/13
- Re: [Qemu-devel] [question] is it possible that big-endian l1 tableoffsetreferencedby other I/O while updating l1 table offset in qcow2_update_snapshot_refcount?, Zhang Haoyu, 2014/10/13
- Re: [Qemu-devel] [question] is it possible that big-endian l1 tableoffsetreferencedby other I/O while updating l1 table offset in qcow2_update_snapshot_refcount?, Max Reitz, 2014/10/13
- Re: [Qemu-devel] [question] is it possible that big-endian l1tableoffsetreferencedby other I/O while updating l1 table offset inqcow2_update_snapshot_refcount?, Zhang Haoyu, 2014/10/13