While benchmarking a Win10 VM in PVE 6.3-4 with CrystalDiskMark I got kernel panics (Out of Memory). This happend every time I tried the benchmark. Looking at htop it was surely a RAM memory related issue. I first thought it was an over-assigning problem with my memory to VM's or a ballooning...
I searched this forum and google but i cannot find the final aswer..
We have a Proxmox cluster with a remote Ceph Luminous cluster.
I see i get muge faster writes with Cache=writeback in the disk options in Proxmox, (random 4k up to 16x faster and Seq 10x faster) then with cache=none...
I have installed Proxmox with ZFS RAID Z1.
I have a doubt.
In a KVM Virtio, always use VirtIO = Write Back.
But doing tests, I see Default(no cache). It is much faster write speed.
test: dd if=/dev/zero of=test bs=64k count=16k conv=fdatasync
cache: none = 1073741824...