Basic Multipath Question - Please help clear up some confusion

[lamotta]

I have recently set up a new storage array ( Dell MD3200) to complement our existing array. However when pointing to the target array via the Proxmox storage config we are only pointing to one of the IP addresses configured on one of the storage controllers. This is how the existing array is configured and I am told that multipathing works. But I don't understand how this can be. If the port of the storage controller which is configured with the IP address that proxmox points to were to fail then surely connectivity to the storage array would fail thus presenting a single point of failure.

If anyone can clear up my confusion then that would be greatly appreciated.

Thanks

 

[tom]

I assume you know this page?
http://pve.proxmox.com/wiki/ISCSI_Multipath

 

[lamotta]

Yep - have read through it. No exceptions have been set up but the multipath -ll command does appear to show that multipath is running. I haven't tested it yet but I am sure once I disable the port on the storage array which proxmox points to that connectivity to the storage will fail?

 

[lamotta]

I have just disabled the port on the controller. So for example proxmox points to 10.10.1.1 on the storage array. The storage array in turn presents storage to proxmox. Multipathing is enabled, I have just disabled the port configured with 10.10.1.1 and data on the storage array is still accessible. Would love to understand how this is working.

 

[tom]

multipath means there are more connections - redundancy. so if you cut one line, the second one is still there. what is unclear?

 

[lamotta]

Hi - thanks for your reply. I understand what Multipath means. I just don't understand how multipathing works when the proxmox host points to the storage array via a single ip address (portal). If I disable the port with the associated IP on the storage array - the VMs utilising storage on the array still work. How is this so when the IP proxmox is pointing to for the array is no longer accessible?

 

[hotwired007]

the other IP addresses are passed into the multipath config when you configure the storage - although proxmox only sees the one IP, the others are in the config