[pve-devel] [PATCH] Add Multipath direct storage plugin and enable it.

[Dmitry Petuhov]

29.06.2016 17:59, Dmitry Petuhov wrote:
> Yes, it may pass almost any disk, visible to host, to VM. Even if disk does not have own WWN ([s]ata/virtual/etc disks), Linux generates it using some unique disk identifiers, like SN. This feature is sometimes useful too. In worst case, there's some host-unique ids like wwn-0xQEMU_QEMU_HARDDISK_drive-scsi0.
>
> Real problem is that we cannot distinguish between local-only and shared disks. That's actually OK for single-host setups, but is dangerous in clusters. I'll try to find out how to manage this.
>
> Maybe we could share which WWN is visible by which host via pmxcfs? Also, we could store here which WWN belongs to which VM, preventing accidental lun sharing. 
Got idea.
Multipath layer sees only WWN of LUN. But SAN knows also image name, which can be like we love: vm-$vmid-disk-$num. So, using LunCmd modules, we can associate WWN with image name and work in each storage instance only with LUNs, for which we can find such associations on particular SAN. For unsupported SANs (or, say, to connect some host's local disks to VMs), we always can have manual associations via file in pmxcfs.