I admin a number of Dell branded E2660 and E2760 units (MD3660f and MD3860f), and I am looking at recommending a pair of E5660 units for purchase. Dell is discontinuing the line, and has never sold the "bigger/better" units.
One shortcoming of the Dell branded units is that adding an enclosure requires an outage for the unit. You are directed to power the array off, cable the new enclosure, and power it all back up. I have a number of other arrays (EMC, IBM, etc.) that do not have this restriction including some IBM branded Engenio designs.
I am wondering: in the E5660, is that also the basic upgrade plan, or can an enclosure be added to a running system? I am looking at configuring two E5660s with each one having a pair of 60 disk enclosures attached and I want to be sure that I understand whether we would face the same restrictions that we currently have on our smaller units. I got the hint in the 'glossy' materials that they can be expanded while in use, but I am expereinced enough to at least ask for confirmation. I would hate to have to take over half a PB of LUNs down just to add another tray six omnths or a year down the road.
Refer Adding a drive tray to an existing storage array You can add a new drive tray while power is still applied to the other components of the storage array. You can configure, reconfigure, add, or relocate storage array capacity without interrupting user access to data. on page 108
Refer Connecting the drive tray You may add a new drive tray while power is still applied to the other components of the storage array so that access to data is not interrupted. on page 110