The QEMU project is currently moving its bug tracking to another system.
For this we need to know which bugs are still valid and which could be
closed already. Thus we are setting the bug state to "Incomplete" now.
If the bug has already been fixed in the latest upstream version of QEMU,
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for this problem in our new tracker here:
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Thank you and sorry for the inconvenience.
** Tags added: feature-request
** Changed in: qemu
Status: New => Incomplete
** Changed in: qemu
Importance: Undecided => Wishlist
--
You received this bug notification because you are a member of qemu-
devel-ml, which is subscribed to QEMU.
https://bugs.launchpad.net/bugs/1920211
Title:
shrink option for discard (for bad host-filesystems and -backup
solutions)
Status in QEMU:
Incomplete
Bug description:
When using discard=unmap for virtio or scsi devices with QCOW2 images,
space discarded by the guest will be unmaped on the host, which is
basically great!
This will turn the QCOW2 image into a sparse file which is efficient
for most scenarios. But it may be that you need to avoid big sparse
files on your host. For example because you need to use a backup
solution which doesn't support sparse files well. Or maybe the QCOW2
image is on a filesystem mount which doesn't support sparse files at
all.
For those scenarios an alternative option for the discard setting
(discard=shrink) would be great, so that the QCOW2 file itself gets shrunken
again.
I'm not sure about how the initial growing* of QCOW2 images is implemented
and if there are maybe limitations. But I hope it may be possible do the
inverse and actually shrink (not sparse) an QCOW2 image with internally
discarded blocks.
I'm using Qemu-5.2.0 and Linux >= 5.3 (host and guest).
*If you use "qemu-img create -f qcow2 ..." withOUT the "preallocation"
option.
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