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[Qemu-devel] qemu-img problem when create a file larger than fs's size
From: |
yuxh |
Subject: |
[Qemu-devel] qemu-img problem when create a file larger than fs's size |
Date: |
Wed, 08 May 2013 13:18:17 +0800 |
User-agent: |
Mozilla/5.0 (X11; Linux x86_64; rv:10.0.5) Gecko/20120607 Thunderbird/10.0.5 |
Hello all,
I have to consult you a qemu-img's problem.
Is this reasonable to create a file which is larger than the available
size of the fs by qemu-img cmd ?
When I use qemu-img create a file which is larger than the available
size of the fs, the creation is completed succesfully.
However when I use this file in guest as a guest's disk, and write
beyond the size the host file can provides, the guest was paused by
qemu-kvm or libvirt and was in maybe a infinite circle where the guest
just can't be used except I detach the disk from guest or destroy the guest.
I read the qemu-img's code and found it just create the file as we
required and doesn't check if the size we specify is reasonable.But this
may let the guest in a risk of meeting the problem I describe above.
Exp:
address@hidden mytest]# df -ah /mytest/
Filesystem Size Used Avail Use% Mounted on
/dev/sdb2 2.0G 3.1M 1.9G 1% /mytest
address@hidden mytest]# qemu-img create -f raw test.raw 3G
Formatting 'test.raw', fmt=raw size=3221225472
address@hidden mytest]# ls -l test.raw
-rw-r--r--. 1 root root 3221225472 May 8 12:23 test.raw
address@hidden mytest]#
Thank you.
Best Regards
Xinghai Yu