[ovirt-users] Re: about the vm disk type

For example : And I check the file on the storage: [root@olvms1 51dcbfae-1100-4e43-9e0a-bb8c578623d7]# cat 9e4dc022-c450-4f85-89f5-233fa41c07d0.meta CAP=10737418240 CTIME=1632305740 DESCRIPTION={"DiskAlias":"test09222_Disk1","DiskDescription":""} DISKTYPE=DATA DOMAIN=f77091d9-aabc-42db-87b1-b8299765482e *FORMAT=RAW* GEN=0 IMAGE=51dcbfae-1100-4e43-9e0a-bb8c578623d7 LEGALITY=LEGAL PUUID=00000000-0000-0000-0000-000000000000 TYPE=SPARSE VOLTYPE=LEAF EOF [root@olvms1 51dcbfae-1100-4e43-9e0a-bb8c578623d7]# [root@olvms1 51dcbfae-1100-4e43-9e0a-bb8c578623d7]# [root@olvms1 51dcbfae-1100-4e43-9e0a-bb8c578623d7]# ll total 1025 -rw-rw----. 1 vdsm kvm 10737418240 Sep 22 18:15 9e4dc022-c450-4f85-89f5-233fa41c07d0 -rw-rw----. 1 vdsm kvm 1048576 Sep 22 18:15 9e4dc022-c450-4f85-89f5-233fa41c07d0.lease -rw-r--r--. 1 vdsm kvm 303 Sep 22 18:15 9e4dc022-c450-4f85-89f5-233fa41c07d0.meta [root@olvms1 51dcbfae-1100-4e43-9e0a-bb8c578623d7]# [root@olvms1 51dcbfae-1100-4e43-9e0a-bb8c578623d7]# [root@olvms1 51dcbfae-1100-4e43-9e0a-bb8c578623d7]# du -h ./9e4dc022-c450-4f85-89f5-233fa41c07d0 0 ./9e4dc022-c450-4f85-89f5-233fa41c07d0 [root@olvms1 51dcbfae-1100-4e43-9e0a-bb8c578623d7]# [root@olvms1 51dcbfae-1100-4e43-9e0a-bb8c578623d7]# -----Original Message----- From: users-bounces(a)ovirt.org <users-bounces(a)ovirt.org&gt; On Behalf Of Tommy Sway Sent: Wednesday, September 22, 2021 6:07 PM To: 'Vojtech Juranek' <vjuranek(a)redhat.com>; users(a)ovirt.org Subject: [ovirt-users] Re: about the vm disk type You mean if it's pre-allocated, it must be RAW, not Qcow2? The documentation only states that RAW must be pre-allocated, but it does not say that qCOW2 cannot use pre-allocation. -----Original Message----- From: Vojtech Juranek <vjuranek(a)redhat.com&gt; Sent: Wednesday, September 22, 2021 6:04 PM To: users(a)ovirt.org Cc: Tommy Sway <sz_cuitao(a)163.com&gt; Subject: Re: [ovirt-users] about the vm disk type On Wednesday, 22 September 2021 09:55:26 CEST Tommy Sway wrote: > When I create the VM's image disk, I am not asked to select the > following type of disk. Actually you are, it's "Allocation Policy" drop down menu. Thin provisioned == qcow format Preallocated == raw > > > What is the default value ? Thin provisioned, i.e. qcow. > > > Thanks. > > > > > > QCOW2 Formatted Virtual Machine Storage > > QCOW2 is a storage format for virtual disks. QCOW stands for QEMU > copy-on-write. The QCOW2 format decouples the physical storage layer > from the virtual layer by adding a mapping between logical and > physical blocks. > Each logical block is mapped to its physical offset, which enables > storage over-commitment and virtual machine snapshots, where each QCOW > volume only represents changes made to an underlying virtual disk. > > The initial mapping points all logical blocks to the offsets in the > backing file or volume. When a virtual machine writes data to a QCOW2 > volume after a snapshot, the relevant block is read from the backing > volume, modified with the new information and written into a new > snapshot QCOW2 volume. Then the map is updated to point to the new place. > > Raw > > The raw storage format has a performance advantage over QCOW2 in that > no formatting is applied to virtual disks stored in the raw format. > Virtual machine data operations on virtual disks stored in raw format > require no additional work from hosts. When a virtual machine writes > data to a given offset in its virtual disk, the I/O is written to the > same offset on the backing file or logical volume. > > Raw format requires that the entire space of the defined image be > preallocated unless using externally managed thin provisioned LUNs > from a storage array. _______________________________________________ Users mailing list -- users(a)ovirt.org To unsubscribe send an email to users-leave(a)ovirt.org Privacy Statement: https://www.ovirt.org/privacy-policy.html oVirt Code of Conduct: https://www.ovirt.org/community/about/community-guidelines/ List Archives: https://lists.ovirt.org/archives/list/users@ovirt.org/message/JGJX4VUOYVB... _______________________________________________ Users mailing list -- users(a)ovirt.org To unsubscribe send an email to users-leave(a)ovirt.org Privacy Statement: https://www.ovirt.org/privacy-policy.html oVirt Code of Conduct: https://www.ovirt.org/community/about/community-guidelines/ List Archives: https://lists.ovirt.org/archives/list/users@ovirt.org/message/JMXUYJXYWNH...