Drobo 5D in Read Only. MacOSX says cannot repair drive. Get a new drobo 5d3?

Hi! I have a pretty old (2016) Drobo 5D that has been great until two days ago. It went into read only mode with all green lights and now Mac OSX says cannot repair.

I am not sure if I need a new Drobo 5D3 and can insert my drives into the new device. Or if I need all new drives as well? Any insight is appreciated.

I have a backup of the drobo, but would prefer to migrate the data for extra pre-caution to a new system/drive before reformatting anything.

Well Drobo’s insight is here: Drobo is suddenly read-only

Note the last option:

  • If none of the above resolves. Copy off the data and reformat.

I suspect trying to migrate directly will probably result in the pack remaining read-only, but that’s just a “best guess” on my part.

A reformat or factory reset, followed by restoring your data from backup is highly likely to resolve it without a new Drobo, unless you need one in order to store a backup.

@cyber_beardy thanks for your opinion! It’s helpful! I am working on a solution to copy off the 30TB of data before reformatting and see where that takes me! Will report back.

@cyber_beardy I ended up resetting the drives and restoring drobo. All the lights are green, but it says capacity 28TB when there should be 42tb (8+8+8+8+10). Is that a sign a drive has actually failed? Or that the drobo itself is broken? Im so confused.

Seems not far off to me looking at the capacity calculator
Capacity Calculator - Drobo

The “rule of thumb” tends to be capacity of drives minus biggest drive & again that would give a capacity (raw) of 32TB minus formatting overhead & again seems roughly right.

Based on that I deduce you’re only using single drive redundancy, personally I’d consider that unwise with large drives (for this purpose “large” means bigger than about 4TB, above that the chance of an unrecoverable read error (and data loss) during a rebuild becomes unacceptably high.

Just to confirm you did not run into a firmware/OSX issue, did you test to connect it via a different IO? If you use thunderbolt, try USB 3 for example.


Screen Shot 2021-04-22 at 7.02.06 AM

I’m confused my MacOSX says Drobo has 70TB and 56TB free?? And then Drobo Dashboard says differently. The good thing is the reformat got the Drobo off read only.

I have a synology nas, cloud backup and now Gdrive all with a copy of this data as well. So its ok that I just do the single redundancy right?

Welcome to thin provisioning your Mac is reporting the size of the filesystem it sees which is something like 64TiB by default, the Drobo is reporting the storage it actually has, & will ask for bigger disks when needed in order to actually provide the space your Mac reports.

This is perfectly normal, expected, & one of the features of Drobos, allowing you to expand without having to backup/reformat, & restore every time your storage expands.

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