Re: [Qemu-devel] qemu-img problem when create a file larger than fs's size
On 05/09/2013 03:44 PM, Stefan Hajnoczi wrote: On Wed, May 08, 2013 at 01:18:17PM +0800, yuxh wrote: 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. You can change the ENOSPC policy with -drive werror=,rerror=. See the QEMU man page. The default behavior is to pause the guest so the host admin can free up or add space. Then the guest can be continued - this will retry the I/O. But you can also tell QEMU to pass the error through to the guest using the -drive werror=,rerror= options. Stefan Oh, understand now. Thank you so much for your explanation. Yu
Re: [Qemu-devel] qemu-img problem when create a file larger than fs's size
On Wed, May 08, 2013 at 01:18:17PM +0800, yuxh wrote: > 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. You can change the ENOSPC policy with -drive werror=,rerror=. See the QEMU man page. The default behavior is to pause the guest so the host admin can free up or add space. Then the guest can be continued - this will retry the I/O. But you can also tell QEMU to pass the error through to the guest using the -drive werror=,rerror= options. Stefan
Re: [Qemu-devel] qemu-img problem when create a file larger than fs's size
On 05/08/2013 04:20 PM, Fam Zheng wrote: On Wed, 05/08 15:34, yuxh wrote: Thank you for your reply. I agreed what you said. And do you think we shall print a prompt to user when the size user specified is larger than available space ? Might be nice, but it's hard to define "available space", and "available space" at creating time promises nothing. Even if the user creates a small image which seems safe, risk is still there: when other applications' data fills up the "available space", the use still experiences the same problem. Yes. That means the prompt means nothing. Thank you very much! yuxh On 05/08/2013 02:36 PM, Fam Zheng wrote: I think it's the system admin to be responsible for the risk of over provisioning. We have host sparse file[1] (as your example) for preallocated image (for example, -f raw), as well as sparse image (as supported in qcow2, vmdk, etc.). There are cases that host file system is extended or the vm disk is moved to a larger storage when the actual data grows closer to full, so it's not very practical to limit the creating size, just as this is quietly valid in linux, no matter how small your /tmp is. # df /tmp/ -h Filesystem Size Used Avail Use% Mounted on tmpfs 3.8G 14M 3.8G 1% /tmp # touch /tmp/a # truncate /tmp/a --size 1T # ls -l /tmp/a -rw-rw-r--. 1 fam fam 1099511627776 May 8 14:33 /tmp/a [1]: http://en.wikipedia.org/wiki/Sparse_file On Wed, 05/08 13:18, yuxh wrote: 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: [root@build mytest]# df -ah /mytest/ FilesystemSize Used Avail Use% Mounted on /dev/sdb2 2.0G 3.1M 1.9G 1% /mytest [root@build mytest]# qemu-img create -f raw test.raw 3G Formatting 'test.raw', fmt=raw size=3221225472 [root@build mytest]# ls -l test.raw -rw-r--r--. 1 root root 3221225472 May 8 12:23 test.raw [root@build mytest]# Thank you. Best Regards Xinghai Yu -- 以上 第一软件事业部 第一开发部 driver组 于星海 Best Regards -- Yu Xinghai Development Dept.I Nanjing Fujitsu Nanda Software Tech. Co., Ltd.(FNST) No.6 Wenzhu Road, Nanjing, 210012, China TEL: +86+25-86630566-8533 FUJITSU INTERNAL: 7998-8533 FAX: +86+25-83317685 MAIL: yuxing...@cn.fujitsu.com -- -- 以上 第一软件事业部 第一开发部 driver组 于星海 Best Regards -- Yu Xinghai Development Dept.I Nanjing Fujitsu Nanda Software Tech. Co., Ltd.(FNST) No.6 Wenzhu Road, Nanjing, 210012, China TEL: +86+25-86630566-8533 FUJITSU INTERNAL: 7998-8533 FAX: +86+25-83317685 MAIL: yuxing...@cn.fujitsu.com --
Re: [Qemu-devel] qemu-img problem when create a file larger than fs's size
On Wed, 05/08 15:34, yuxh wrote: > > Thank you for your reply. I agreed what you said. > And do you think we shall print a prompt to user when the size user > specified is larger than available space ? Might be nice, but it's hard to define "available space", and "available space" at creating time promises nothing. Even if the user creates a small image which seems safe, risk is still there: when other applications' data fills up the "available space", the use still experiences the same problem. > > On 05/08/2013 02:36 PM, Fam Zheng wrote: > >I think it's the system admin to be responsible for the risk of over > >provisioning. We have host sparse file[1] (as your example) for > >preallocated image (for example, -f raw), as well as sparse image (as > >supported in qcow2, vmdk, etc.). There are cases that host file system > >is extended or the vm disk is moved to a larger storage when the actual > >data grows closer to full, so it's not very practical to limit the > >creating size, just as this is quietly valid in linux, no matter how > >small your /tmp is. > > > > # df /tmp/ -h > > Filesystem Size Used Avail Use% Mounted on > > tmpfs 3.8G 14M 3.8G 1% /tmp > > # touch /tmp/a > > # truncate /tmp/a --size 1T > > # ls -l /tmp/a > > -rw-rw-r--. 1 fam fam 1099511627776 May 8 14:33 /tmp/a > > > >[1]: http://en.wikipedia.org/wiki/Sparse_file > > > >On Wed, 05/08 13:18, yuxh wrote: > >>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: > >>[root@build mytest]# df -ah /mytest/ > >>FilesystemSize Used Avail Use% Mounted on > >>/dev/sdb2 2.0G 3.1M 1.9G 1% /mytest > >>[root@build mytest]# qemu-img create -f raw test.raw 3G > >>Formatting 'test.raw', fmt=raw size=3221225472 > >>[root@build mytest]# ls -l test.raw > >>-rw-r--r--. 1 root root 3221225472 May 8 12:23 test.raw > >>[root@build mytest]# > >> > >>Thank you. > >> > >>Best Regards > >>Xinghai Yu > >> > > > > -- > 以上 > > 第一软件事业部 第一开发部 driver组 于星海 > Best Regards > -- > Yu Xinghai > Development Dept.I > Nanjing Fujitsu Nanda Software Tech. Co., Ltd.(FNST) > No.6 Wenzhu Road, Nanjing, 210012, China > TEL: +86+25-86630566-8533 > FUJITSU INTERNAL: 7998-8533 > FAX: +86+25-83317685 > MAIL: yuxing...@cn.fujitsu.com > -- -- Fam
Re: [Qemu-devel] qemu-img problem when create a file larger than fs's size
Thank you for your reply. I agreed what you said. And do you think we shall print a prompt to user when the size user specified is larger than available space ? On 05/08/2013 02:36 PM, Fam Zheng wrote: I think it's the system admin to be responsible for the risk of over provisioning. We have host sparse file[1] (as your example) for preallocated image (for example, -f raw), as well as sparse image (as supported in qcow2, vmdk, etc.). There are cases that host file system is extended or the vm disk is moved to a larger storage when the actual data grows closer to full, so it's not very practical to limit the creating size, just as this is quietly valid in linux, no matter how small your /tmp is. # df /tmp/ -h Filesystem Size Used Avail Use% Mounted on tmpfs 3.8G 14M 3.8G 1% /tmp # touch /tmp/a # truncate /tmp/a --size 1T # ls -l /tmp/a -rw-rw-r--. 1 fam fam 1099511627776 May 8 14:33 /tmp/a [1]: http://en.wikipedia.org/wiki/Sparse_file On Wed, 05/08 13:18, yuxh wrote: 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: [root@build mytest]# df -ah /mytest/ FilesystemSize Used Avail Use% Mounted on /dev/sdb2 2.0G 3.1M 1.9G 1% /mytest [root@build mytest]# qemu-img create -f raw test.raw 3G Formatting 'test.raw', fmt=raw size=3221225472 [root@build mytest]# ls -l test.raw -rw-r--r--. 1 root root 3221225472 May 8 12:23 test.raw [root@build mytest]# Thank you. Best Regards Xinghai Yu -- 以上 第一软件事业部 第一开发部 driver组 于星海 Best Regards -- Yu Xinghai Development Dept.I Nanjing Fujitsu Nanda Software Tech. Co., Ltd.(FNST) No.6 Wenzhu Road, Nanjing, 210012, China TEL: +86+25-86630566-8533 FUJITSU INTERNAL: 7998-8533 FAX: +86+25-83317685 MAIL: yuxing...@cn.fujitsu.com --
Re: [Qemu-devel] qemu-img problem when create a file larger than fs's size
I think it's the system admin to be responsible for the risk of over provisioning. We have host sparse file[1] (as your example) for preallocated image (for example, -f raw), as well as sparse image (as supported in qcow2, vmdk, etc.). There are cases that host file system is extended or the vm disk is moved to a larger storage when the actual data grows closer to full, so it's not very practical to limit the creating size, just as this is quietly valid in linux, no matter how small your /tmp is. # df /tmp/ -h Filesystem Size Used Avail Use% Mounted on tmpfs 3.8G 14M 3.8G 1% /tmp # touch /tmp/a # truncate /tmp/a --size 1T # ls -l /tmp/a -rw-rw-r--. 1 fam fam 1099511627776 May 8 14:33 /tmp/a [1]: http://en.wikipedia.org/wiki/Sparse_file On Wed, 05/08 13:18, yuxh wrote: > 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: > [root@build mytest]# df -ah /mytest/ > FilesystemSize Used Avail Use% Mounted on > /dev/sdb2 2.0G 3.1M 1.9G 1% /mytest > [root@build mytest]# qemu-img create -f raw test.raw 3G > Formatting 'test.raw', fmt=raw size=3221225472 > [root@build mytest]# ls -l test.raw > -rw-r--r--. 1 root root 3221225472 May 8 12:23 test.raw > [root@build mytest]# > > Thank you. > > Best Regards > Xinghai Yu > -- Fam
[Qemu-devel] qemu-img problem when create a file larger than fs's size
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: [root@build mytest]# df -ah /mytest/ FilesystemSize Used Avail Use% Mounted on /dev/sdb2 2.0G 3.1M 1.9G 1% /mytest [root@build mytest]# qemu-img create -f raw test.raw 3G Formatting 'test.raw', fmt=raw size=3221225472 [root@build mytest]# ls -l test.raw -rw-r--r--. 1 root root 3221225472 May 8 12:23 test.raw [root@build mytest]# Thank you. Best Regards Xinghai Yu
