Bug 806312 - block stream touches all qcow2 image cluster
block stream touches all qcow2 image cluster
Product: Red Hat Enterprise Linux 6
Classification: Red Hat
Component: qemu-kvm (Show other bugs)
Unspecified Unspecified
medium Severity medium
: rc
: ---
Assigned To: Virtualization Maintenance
Virtualization Bugs
Depends On:
Blocks: 806280
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Reported: 2012-03-23 08:16 EDT by Shaolong Hu
Modified: 2012-03-23 09:41 EDT (History)
7 users (show)

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Fixed In Version:
Doc Type: Bug Fix
Doc Text:
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Clone Of:
Last Closed: 2012-03-23 09:41:04 EDT
Type: ---
Regression: ---
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RHEL 7.3 requirements from Atomic Host:
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Description Shaolong Hu 2012-03-23 08:16:46 EDT
Description of problem:
After block stream, qcow2 image disk size reaches to virtual size.

Version-Release number of selected component (if applicable):

How reproducible:

Steps to Reproduce:
1.(qemu) info block
drive-virtio-disk0: removable=0 io-status=ok file=/root/RHEL-Server-6.3-64-virtio.qcow2 ro=0 drv=qcow2 encrypted=0

2.(qemu) snapshot_blkdev drive-virtio-disk0 /root/sn1 qcow2

3.(qemu) block_stream drive-virtio-disk0

4.[root@shu ~]# qemu-img info sn1
image: sn1
file format: qcow2
virtual size: 20G (21474836480 bytes)
disk size: 20G
cluster_size: 65536

5.[root@shu ~]# qemu-img info RHEL-Server-6.3-64-virtio.qcow2 
image: RHEL-Server-6.3-64-virtio.qcow2
file format: qcow2
virtual size: 20G (21474836480 bytes)
disk size: 4.5G
cluster_size: 65536

Expected results:
Hi, i am not sure whether this is a bug, if not, please explain a little bit, and i highly recommend this as a RFE if can not be solved in 6.3, for streaming is mainly used by customer to update or re-arrange their storage, they probably don't want to see that after migrating to a larger storage, there is still no space left.
Comment 2 Kevin Wolf 2012-03-23 09:41:04 EDT
This is expected, only QED supports streaming efficiently today. We will fix this with an image format extension ("qcow3") in RHEL 7.

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