Hello everyone, I just got to work on a daisy chain unified setup with Dell Powervault MD 1200, it was an interesting experience,so I thought to blog it.
Compute : 3 x Dell Poweredge R720 with dual Perc H810 HBA cards .
Storage : 4 x Dell Powervault MD1200 with dual Enclosure Management Modules (EMM), 12 x 1.2TB 10k 3.5″ HDDs with 4GB controller cache
High availability for the application at the compute layer is achieved through a hardware load balancer. I/O redundancy is achieved through SAS multipathing in I/O round robin load balancing mode.
MD 1200 Enclosure Management Module
If you have only one EMM module, then it needs to be installed on the primary slot. An EMM blank needs to be inserted on the secondary slot to preserve cooling. In most cases, for redundancy reasons, you might have two EMM modules. You could connect the enclosures in 3 modes – daisy chain non redundant mode, redundant mode and split mode. The mode is selected via the mode switch on the front of the enclosure. You need to select the mode before powering on the enclosure, otherwise a reboot is required for the mode change.
The IN port of the primary module should be connected to the uplink, for the first enclosure it’s the host. The OUT port goes to the downlink enclosures. The same follows for the secondary EMM as well to achieve IO redundancy.
You can have upto 8 non-redundant enclosures connected to a single host controller card in a daisy chained way. With redundancy, the maximum enclosures will be 4.
The host OMSA can manage all the drives – both internal and external.
- Use the latest version of OMSA on the host.
- During power on, boot up the last enclosure in the chain first and make sure all the status LEDs are green. Then boot up it’s upstream enclosure, and finally the host.
- You can use Windows provided multipath drivers, but it is recommended to use the host multipath drivers available along with Dell MD Storage Manager.
- Select the mode of multipathing of the VD under the multipath device properties in Device Management.
- Make sure to close all open HDD bays with carrier blank caddices to preserve cooling.
- Have a practice to lock the front Bezel for additional security.
More details at