[ovirt-users] preallocated storage issue?
Fred Rolland
frolland at redhat.com
Sun Aug 7 09:55:27 UTC 2016
Simon,
What is happening is that when we create a preallocated disk on NFS, we
fill the file with zeros in order to "allocate" the space.
However, while copying the disk we use qemu-img that will ignore the zeros.
Quick way to demonstrate:
[root at white-vdsd test]# dd if=/dev/zero of=myfile.txt bs=1M count=1
1+0 records in
1+0 records out
1048576 bytes (1.0 MB, 1.0 MiB) copied, 0.00172084 s, 609 MB/s
[root at white-vdsd test]# du -h myfile.txt
1.0M myfile.txt
[root at white-vdsd test]# ls -lh myfile.txt
-rw-r--r-- 1 root root 1.0M Aug 7 12:39 myfile.txt
[root at white-vdsd test]# qemu-img convert myfile.txt myfile2.txt
[root at white-vdsd test]# ls -lh myfile2.txt
-rw-r--r-- 1 root root 1.0M Aug 7 12:41 myfile2.txt
[root at white-vdsd test]# du -h myfile2.txt
0 myfile2.txt
[root at white-vdsd test]# qemu-img info myfile.txt
image: myfile.txt
file format: raw
virtual size: 1.0M (1048576 bytes)
disk size: 1.0M
[root at white-vdsd test]# qemu-img info myfile2.txt
image: myfile2.txt
file format: raw
virtual size: 1.0M (1048576 bytes)
disk size: 0
I hope this explains what you see.
Regards,
Fred
On Sun, Aug 7, 2016 at 11:13 AM, Simon Barrett <
Simon.Barrett at tradingscreen.com> wrote:
> Storage is NFS. What logs would you like to see?
>
> Many thanks.
>
> Simon
>
>
>
> On Sun, Aug 7, 2016 at 8:53 AM +0100, "Fred Rolland" <frolland at redhat.com>
> wrote:
>
> Simon hi,
>
> What storage type are you using in source and target storage domains ?
> (NFS, ISCSI....)
>
> Can you share the logs?
>
> Thanks,
> Fred
>
> On Fri, Aug 5, 2016 at 6:37 PM, Simon Barrett <
> Simon.Barrett at tradingscreen.com> wrote:
>
>> Another example. This one was moved to a new storage domain
>>
>>
>>
>> root at ovirt_host1> qemu-img info dd6f25f6-7830-4024-915f-a20268797c34
>>
>> image: dd6f25f6-7830-4024-915f-a20268797c34
>>
>> file format: raw
>>
>> virtual size: 200G (214748364800 bytes)
>>
>> disk size: 5.0G
>>
>>
>>
>> root@ ovirt_host1> cat dd6f25f6-7830-4024-915f-a20268797c34.meta
>>
>> DOMAIN=53560d43-874a-49c5-9c5a-8b90487c79f8
>>
>> VOLTYPE=LEAF
>>
>> CTIME=1470305678
>>
>> FORMAT=RAW
>>
>> IMAGE=741976cd-d1cb-4031-bdbe-6a745dff16ef
>>
>> DISKTYPE=2
>>
>> PUUID=00000000-0000-0000-0000-000000000000
>>
>> LEGALITY=LEGAL
>>
>> MTIME=0
>>
>> POOL_UUID=
>>
>> SIZE=419430400
>>
>> TYPE=PREALLOCATED
>>
>> DESCRIPTION=
>>
>> EOF
>>
>>
>>
>>
>>
>> This one has not been moved:
>>
>>
>>
>> root at ny2-lvb-066.mgt> qemu-img info 155f0d33-c280-4236-8d1e-fcb88f9a1242
>>
>> image: 155f0d33-c280-4236-8d1e-fcb88f9a1242
>>
>> file format: raw
>>
>> virtual size: 90G (96636764160 bytes)
>>
>> disk size: 90G
>>
>>
>>
>> root at ny2-lvb-066.mgt> cat 155f0d33-c280-4236-8d1e-fcb88f9a1242.meta
>>
>> DOMAIN=59bde2ff-e10d-477e-91c1-6355abff0999
>>
>> CTIME=1464946639
>>
>> FORMAT=RAW
>>
>> DISKTYPE=2
>>
>> LEGALITY=LEGAL
>>
>> SIZE=188743680
>>
>> VOLTYPE=LEAF
>>
>> DESCRIPTION={"DiskAlias":"ny2-laa-010.prod_Disk1","DiskDescription":""}
>>
>> IMAGE=82158182-81a4-458e-a41b-663756962666
>>
>> PUUID=00000000-0000-0000-0000-000000000000
>>
>> MTIME=0
>>
>> POOL_UUID=
>>
>> TYPE=PREALLOCATED
>>
>> EOF
>>
>>
>>
>> See the mismatch between “virtual size” and “disk size” on the one that
>> was moved.
>>
>>
>>
>> TIA,
>>
>>
>>
>> Simon
>>
>>
>>
>> *From:* users-bounces at ovirt.org [mailto:users-bounces at ovirt.org] *On
>> Behalf Of *Simon Barrett
>> *Sent:* Friday, 5 August, 2016 10:25
>> *To:* users at ovirt.org
>> *Subject:* [ovirt-users] preallocated storage issue?
>>
>>
>>
>> If I create a preallocated disk for a VM, I see the disk image file
>> listing as the size I requested (100G):
>>
>>
>>
>> cd /rhev/data-center/mnt/storage_host1:_vol_pa1__nas__01b__oVir
>> t__prod__01/53560d43-874a-49c5-9c5a-8b90487c79f8/images/d97f
>> 7706-3662-40bf-9358-80e0dc51bff4
>>
>> root at ovirt_host> ls -l
>>
>> total 105064644
>>
>> -rw-rw---- 1 vdsm kvm 107374182400 Aug 5 10:57
>> 75c14559-e18f-4cc8-a3fe-bc0de507720b
>>
>> -rw-rw---- 1 vdsm kvm 1048576 Aug 5 10:57
>> 75c14559-e18f-4cc8-a3fe-bc0de507720b.lease
>>
>> -rw-r--r-- 1 vdsm kvm 313 Aug 5 10:57
>> 75c14559-e18f-4cc8-a3fe-bc0de507720b.meta
>>
>>
>>
>> and the corresponding space used on disk matches
>>
>>
>>
>> root@ ovirt_host > du -sh *
>>
>> 101G 75c14559-e18f-4cc8-a3fe-bc0de507720b
>>
>> 1.1M 75c14559-e18f-4cc8-a3fe-bc0de507720b.lease
>>
>> 4.0K 75c14559-e18f-4cc8-a3fe-bc0de507720b.meta
>>
>>
>>
>> If I then migrate that storage (while the VM is shutdown) to a new
>> storage domain, the size on disk does not match the allocated size. In this
>> case there is nothing in the disk yet so it shows as 0.
>>
>>
>>
>> cd /rhev/data-center/mnt/storage_host2:_vol_pa1__ovirt__uatprod
>> /1f2c2b48-1e77-4c98-a6da-5dc09b78cead/images/d97f7706-
>> 3662-40bf-9358-80e0dc51bff4
>>
>> root@ ovirt_host> ls -l
>>
>> total 1032
>>
>> -rw-rw---- 1 vdsm kvm 107374182400 Aug 5 11:06
>> 75c14559-e18f-4cc8-a3fe-bc0de507720b
>>
>> -rw-rw---- 1 vdsm kvm 1048576 Aug 5 11:06
>> 75c14559-e18f-4cc8-a3fe-bc0de507720b.lease
>>
>> -rw-r--r-- 1 vdsm kvm 313 Aug 5 11:06
>> 75c14559-e18f-4cc8-a3fe-bc0de507720b.meta
>>
>>
>>
>> root@ ovirt_host > du -sh *
>>
>> 0 75c14559-e18f-4cc8-a3fe-bc0de507720b
>>
>> 1.1M 75c14559-e18f-4cc8-a3fe-bc0de507720b.lease
>>
>> 4.0K 75c14559-e18f-4cc8-a3fe-bc0de507720b.meta
>>
>>
>>
>> oVirt still lists the disk as preallocated in the GUI but it is in fact
>> thin provisioned.
>>
>>
>>
>> I see the same issue if I clone a preallocated VM. The size on disk ends
>> up being the equivalent of a thin-provisioned disk. I also had the issue
>> when importing VM’s from an export domain when I had selected preallocated
>> in the import dialog box.
>>
>>
>>
>> Is this a known issue? Should preallocated not mean preallocated on
>> physical disk?
>>
>>
>>
>> Ovirt Engine is running 3.6.4.1-1.el6
>>
>>
>>
>> The ovirt nodes are running:
>>
>>
>>
>> OS Version: RHEL - 7 - 2.1511.el7.centos.2.10
>>
>> Kernel Version: 3.10.0 - 327.4.5.el7.x86_64
>>
>> KVM Version: 2.3.0 - 31.el7_2.7.1
>>
>> LIBVIRT Version: libvirt-1.2.17-13.el7_2.2
>>
>> VDSM Version: vdsm-4.17.23.2-0.el7.centos
>>
>> SPICE Version: 0.12.4 - 15.el7
>>
>> GlusterFS Version: [N/A]
>>
>> CEPH Version: librbd1-0.80.7-3.el7
>>
>>
>>
>> Many thanks,
>>
>>
>>
>> Simon
>>
>> _______________________________________________
>> Users mailing list
>> Users at ovirt.org
>> http://lists.ovirt.org/mailman/listinfo/users
>>
>>
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.ovirt.org/pipermail/users/attachments/20160807/07acd68a/attachment-0001.html>
More information about the Users
mailing list