On Wed, Jul 7, 2021 at 5:58 PM <radchenko.anato...@gmail.com> wrote: > With some installations of Ovirt in the configuration of ssd for boot OS and > hdd (4k) for data domain, engine is installed on ssd with a block size of > 512e and then transferred to hdd 4k.
What do we mean by transferring engine to another disk? Engine is installed either on a host, or in a vm. On a vm, it always using sector size of 512 bytes, since we don't support vms with sector size of 4k. If enigne in installed on a host, there is no such thing as "transfer" to another host. You can reinstall engine on another host and restore engine database using a backup. Sector size does not matter in this flow. Sector size for data domain is relevant only for gluster storage or local storage. These are the only storage domain types that can use 4k storage. > and if I wanted to leave the engine on ssd (in a separate partition which > will also have a size of 512e), I encountered an incompatibility error > between block sizes 512 and 4k (example glusterfs or when the data domain was > configured as posix compliant fs). NFS domain passed. > As I understand it, the NFS uses 512e as well as the drivers of the guest > machines, Yes, NFS is always using a sector size of 512 bytes since we don't have any way to detect the underlying device sector size. > and a VM created on a domain with a 4k block will still have 512e. As a > result, we have a block of size 512 in any case. Yes, vms always see sector size of 512 bytes. qemu knows the underlying storage sector size and align I/O requests to the underlying storage sector size. > Does it make sense to use devices with a 4k block at the present time? Is > there any configuration to take advantage of 4K? Yes, the most attractive use case is VDO, which is optimized for 4k sector size. Another use case is having disks with 4k sector size which may be cheaper or easier to get compared with disk supporting 512e. For block storage oVirt does not support devices with 4k sector size yet. Nir _______________________________________________ Users mailing list -- users@ovirt.org To unsubscribe send an email to users-le...@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/MSXWMFISNIVWEEGTMBSM5HQMNAIWFIVB/
