X5670 is very old cpu (= slow for today). Server with such cpu doesn't support 12 Gbps SAS on the disk backplane.
ZFS will comment somebody other, but you need to show perftest/fio at least.
You can compare some things with
https://forum.proxmox.com/threads/proxmox-ve-ceph-benchmark-2023-12-fast-ssds-and-network-speeds-in-a-proxmox-ve-ceph-reef-cluster.137964/unread
Proxmox will wait on boot because it will want to mount/enable encrypted partitions. You will need to use some customization in fstab/systemd to override such workflow for manual unlock.