Does JBOD use the controller?

Hello, Does anyone know if after I format My Cloud Mirror as JBOD, with the controller be necessary in order to recognize the drives? In other words, in JBOD mode, can the controller still fail and effect access to the drives? Thank you!


In JBOD mode you will still see the MCM as a single device on your network, but connected to that will appear two separate and independent drives that you can use as you wish.

Essentially you can think of the controller as a simple and cut-down dedicated use PC, whose only job is to control and act as the connection between the drives (in whatever set-up they may be) and the rest of your network.

Thank you for your reply, Darren. If the controller failed on a RAID 1 or JBOD device, would the data be recoverable by replacing the controller? Also wondering, with RAID 1 and/or JBOD, could the drives be installed in a different hard drive enclosure without a controller and still be readable like regular hard drives (without the connection they have in the RAID enclosure)? I’m assuming the files are complete on each drive, but I could be wrong. Thank you!

JBOD certainly should, and I would expect RAID 1to as well, but I must admit I’ve never actually tried it.

It does of course presume that any failure in the controller doesn’t actually damage the drives or data in the process of failing, which may not always be the case.

Thank you again, Darren :slight_smile:

I had an opportunity to speak with an IT person today, and thought I’d share what I learned. According to that source, with RAID 1, the data is complete on each drive, but with JBOD, the drives are striped, so with JBOD, if the controller goes, data cannot be accessed even with a new controller. With RAID 1, the data can be accessed with a new controller, but you would probably have to send the drive in to WD for repair. Good to know. I’ll stick with RAID 1 for now.

The MCM has 4 modes of operation, RAID 0, RAID 1, spanning and JBOD (from page 89 of the MCM manual).

Two are RAID modes (RAID0 and RAID1), the other two are non-RAID modes, which are normally just called JBOD (“Just a Bunch of Disks”). In general JBOD can be done with striping or without striping (as two independent drives or as one combined drive respectively). The “JBOD” on the MCM is the former, whilst the “spanning” mode is the latter.

It’s that second one that your IT person is referring to, so in this case he’s not quite correct for the mode on the MCM called “JBOD” (he’s referring to the other one). Technically both “JBOD” and “Spanning” are JBOD modes, one using the controller (the spanning one) and one without (the one labelled as JBOD).

Darren, thank you so much for this information. I’m very happy to hear that. So here’s a possibly silly question: With JBOD (not spanning) if the controller went, could I still read the drive as if nothing happened?

That’s my understanding yes, but I must admit thankfully it’s not something I’ve had to put into practice as my MCM is doing sterling service sat in its cupboard. If you have a drive caddy though it’s something that could be tested by popping a drive out of the MCM and into it for a trial.