Dell PowerVault Controllers

PowerVault controllers by family and host interface

Match the replacement to the array family and to the host interface of the controller it replaces: Dell's support matrices define each MD3 model by its interface, and ME4 and ME5 enclosures take controllers in several interface versions.

Dell lists 2GB, 4GB or 8GB of cache for dual-controller MD3400 and MD3800 series arrays, so the cache size on the old controller's label is part of the match. Drives for the same arrays are on PowerVault Hard Drives and PowerVault SSDs, complete systems on Dell PowerVault arrays, and every array brand's controllers under Controllers.

EMMs and IOMs for PowerVault expansion shelves

Expansion shelves run on enclosure management modules (EMMs) or I/O modules (IOMs) rather than RAID controllers, and Dell builds them for the MD1200 and MD1220, MD1400 and MD1420, MD1280, MD2412 and MD2424, MD3060e, and ME412, ME424 and ME484 shelves. Dell's MD3 data sheet lists MD1200 and MD1220 shelves as the way to grow the 2U MD3400 and MD3800 series to 192 drives (past 120 with a premium feature), and the MD3060e as the dense shelf that takes the MD3460, MD3860i and MD3860f to 180. For what a JBOD shelf is and when one makes sense, read What Is JBOD?

Replacing one controller without downtime

In a dual-controller ME4 array you can: Dell's ME4 owner's manual states that controller modules and IOMs are hot-swappable in a dual-controller configuration, so one module can be replaced without halting I/O to disk groups while the partner controller runs the system. Dell's ME5 manual adds three rules: both controllers in an enclosure must be the same model type, a removed module must be replaced within five minutes in a 2U enclosure or seven in a 5U enclosure to prevent overheating, and the system should be checked again after 30 minutes. The 5U ME4084 runs only with two controllers; a single-controller 2U array has no partner to fail over to, so plan a maintenance window there.

Matching firmware on partner controllers

An ME controller pair has to run the same firmware, and the array can handle that for you. Dell's ME4 administrator's guide describes Partner Firmware Update (PFU), enabled by default in dual-controller systems: when firmware is updated on one controller, the system updates the partner automatically, and when one controller is replaced, the surviving controller's firmware can be transferred to the new module whether it arrives with older or newer firmware. Dell recommends leaving PFU enabled unless support directs otherwise.