single proxmox to redundant fibre channel paths

[lethargos]

Hi,
I'm using Proxmox 5 and I'd like to use a SAN as storage for VMs. Proxmox lists all four paths (/dev/sdb-dev/sde) and I'd like to make sure that it doesn't see them as separate. What I did was make use of device mapper - fdisk showed all these four paths + the device mapper (/dev/mapper/name) and I simply created the lvm using dm, instead of any of the four paths (/devsdx). Then I added the storage in the proxmox GUI. My question is, is this safe? How should I go about doing that?
I'm not talking about multipathing. I know I need to configure this within linux, - by default it seems that all 4 paths are set as active, so I'm guessing it load balances on all 4.

 

[dietmar]

I'm not talking about multipathing..

What exactly wrong with multipathing?

 

[LnxBil]

I'm not talking about multipathing. I know I need to configure this within linux, - by default it seems that all 4 paths are set as active, so I'm guessing it load balances on all 4.

Please check with:

multipath -ll

 

[lethargos]

multipath -ll shows 4 paths in service-time 0 policy. So that's fine. fdisk -l lists four storages (sdb-sde), but this storage is also represented by device mapper. So first I renamed this dm name so that I could work with a more friendly name, then I created lvm (down to the volume group) then I added a lvm-thin from the proxmox interface. The proxmox interface sees only the udev naming, not the dm naming. My question is, is this safe? Will proxmox work normally? Is this how you're supposed to do it?

 

[LnxBil]

The imporant thing is that pvs sees only the dm and that you use lvm in PVE (with the correct name).

 

[lethargos]

Proxmox itself (the interface) sees the four paths as four different disks and it doesn't see the dm. The only way I can access the storage through the dm name (/dev/mapper/dm-name) is to create a lvm within linux cli and then add it to proxmox.

 

[LnxBil]

Yes, just create your physical disk directly on the device mapper device and then create a volume group. You can also create it in one step with vgcreate. After that, you can add the LVM directly via the GUI.

 

[lethargos]

What would happen if I used the storage through one of the /dev/sdX? On the one hand, would multipath still work, or would it use only one path?

 

[LnxBil]

What would happen if I used the storage through one of the /dev/sdX? On the one hand, would multipath still work, or would it use only one path?

/dev/sdX is exactly one device/path. If that fails, you have problems.