I think, solution you are looking for is direct disk access. It's possible. I use it for my file server VM (FreeNAS) with five 4TB wd red drives (zfs). Passthrough entire PCI storage card is better, but even cheap server motherboards have 6 sata channels (one for dom0 ssd, and five for file server storage). 
This is my example (and my UUIDs)
mkdir /srv/direct-sata_sr
xe sr-create name-label=”Direct SATA SR” name-description=”SATA links to passthrough direct to VMs” type=udev content-type=disk device-config:location=/srv/direct-sata_sr
New UUID generated on sr creation
ba9b124c-c5ac-2c0b-7b1f-014d9cezzzzz
ln -s /dev/disk/by-id/<disk id> /srv/direct-sata_sr/<disk id>
ln -s /dev/disk/by-id/ata-WDC_WD5000BEVT-26A0RT0_WD-WXE1A10V7603 /srv/direct-sata_sr/ata-WDC_WD5000BEVT-26A0RT0_WD-WXE1A10V7603
xe sr-scan uuid=ba9b124c-c5ac-2c0b-7b1f-014d9cezzzzz
xe vdi-list sr-uuid=ba9b124c-c5ac-2c0b-7b1f-014d9cezzzzz
Good luck.