Bug 806312

Summary: block stream touches all qcow2 image cluster
Product: Red Hat Enterprise Linux 6 Reporter: Shaolong Hu <shu>
Component: qemu-kvmAssignee: Virtualization Maintenance <virt-maint>
Status: CLOSED NOTABUG QA Contact: Virtualization Bugs <virt-bugs>
Severity: medium Docs Contact:
Priority: medium    
Version: 6.3CC: acathrow, bsarathy, juzhang, kwolf, michen, mkenneth, virt-maint
Target Milestone: rc   
Target Release: ---   
Hardware: Unspecified   
OS: Unspecified   
Whiteboard:
Fixed In Version: Doc Type: Bug Fix
Doc Text:
Story Points: ---
Clone Of: Environment:
Last Closed: 2012-03-23 13:41:04 UTC Type: ---
Regression: --- Mount Type: ---
Documentation: --- CRM:
Verified Versions: Category: ---
oVirt Team: --- RHEL 7.3 requirements from Atomic Host:
Cloudforms Team: --- Target Upstream Version:
Embargoed:
Bug Depends On:    
Bug Blocks: 806280    

Description Shaolong Hu 2012-03-23 12:16:46 UTC 
Description of problem:
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After block stream, qcow2 image disk size reaches to virtual size.


Version-Release number of selected component (if applicable):
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qemu-kvm-0.12.1.2-2.262.el6rhev.x86_64


How reproducible:
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100%


Steps to Reproduce:
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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:
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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 13:41:04 UTC 
This is expected, only QED supports streaming efficiently today. We will fix this with an image format extension ("qcow3") in RHEL 7.