[ovirt-users] NFS sync vs async

Hello there, At first I thought I had a performance problem with virtio-scsi on Windows, but after thorough experimentation, I finally found that my performance problem was related to the way I share my storage using NFS. Using the settings suggested on the oVirt website for the /etc/exports file, I implemented the following line: /storage *(rw,sync,no_subtree_check,all_squash,anonuid=36,anongid=36) The underlying filesystem is ext4. In the end, whatever the VM I am running through this NFS export, I get extremely poor write performance, like sub-100 IOPS (my disks usually can do 800-1k). Under the hood, iotop shows that my host IO is all taken up by jbd2, and if I understand correctly, it is the ext4 logging process. I have read that using the "async" option in my NFS export is unsafe, like if my host crashes during a write operation, it could corrupt my VM Disks. What is the best combination of filesystem / settings if I want to go with NFS sync? Is someone getting good performance with the same options as me? if so, why do I get such abysmal IOPS numbers? Thanks! J-F Courteau