I just want know how to check the type. According to what you said, qemU-img info tool was used to query the result. On Block storage, theses are results: if preallocated, the storage format is RAW; If Thin mode, is QCOW2; If the VM is cloned from a template in preallocated mode, the disk consists of two files: the bottom back-end file is RAW, and the front end file is QCOW2. If the vm is cloned from a Thin template, I haven't had time to test this. According to the above classification, the performance of QCOW2 is worse than that of RAW format. Therefore, using preallocation mode for Block storage can not only remove interference at the file system level, but also achieve performance advantages in file types, thus achieving the best I/O effect. The last sentence was the result I really wanted, as I was running IO heavy systems on OLVM. Thank you! -----Original Message----- From: users-bounces@ovirt.org <users-bounces@ovirt.org> On Behalf Of Vojtech Juranek Sent: Wednesday, September 22, 2021 8:00 PM To: Tommy Sway <sz_cuitao@163.com> Cc: 'users' <users@ovirt.org> Subject: [ovirt-users] Re: about the vm disk type Sorry for my misleading previous answer, I thought you are asking how to create pre/thin allocated disk. As for the format, you cannot choose it. As for the defaults, Benny already answered this.
I also have block storage on my environment. How do I observe the type of a vm image (LV)?
What do you exactly mean? Do you ask about image format (raw vs. cow)? If so, you can deduce it from Benny's answer, based on the facts on which domain is disk stored and if it's pre-allocated or not. If you are asking how to check it on the storage, you can check disk metadata or you can use directly qemu- img utility (qemu-img info /path/to/the/disk)