Drobo Read Only


My Drobo S (2 Gen) is stuck in read-only mode. It is 10 years old but still has plenty of spare capacity (4.69 TB free - 74 %). Dashboard is running on 3.5.2. It’s linked to my iMac, which is of a similar age and running on High Sierra (10.13).

The problem first came to light with the failure of Time Machine back-ups (message being: unable to update, disk needs reformatting etc). I can read files but no longer create or update them, and there also appears to have been some data loss. Have tried system shutdown and re-start, but to no effect. Drobo Support advised re-installation of dashboard software (3.5.1) - which I notice seems to be a standard response for MacOs 10.13 - but, again, no effect. I sent them the diagnostic report that can be generated from the dashboard, but it’s unclear whether that was investigated.

My hunch is that this isn’t due to any Drobo disk failure, but the problem does lie in the Drobo rather than Mac area. I have seen some reference to DiskWarrior, which I believe is a directory repair tool, but is this a recognised and safe tool for any Drobo repair ? Would it be better just to get another Drobo ? But can the drives be transferred without data loss/erasure ? Or maybe the machines could be linked (one read-only, the other for updates) ?

Anyway, I’d appreciate any advice you guys can give me on next steps.

Well, the official advice from Drobo is here:
Drobo is suddenly read-only

The page particularly calls out most common with TimeMachine backups & permission issues.

Personally my instinctive response would be to go straight to the last option, backup, reset, reformat, restore.

The pack from a Drobo S can be migrated to a Drobo 5C, S, S2, 5D, 5D3, or 8D if the unit fails, but you’ll be wanting it corrected before trying, I’d not like to think of the possible consequences trying to migrate a pack in the current state.

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Many thanks indeed for your reply. The Drobo “official advice” is interesting: it admits there’s a common problem with Time Machine, yet drobo adverts talk about them being “a perfect pairing” !! The first advice about Mac’s Disk Utility was soon answered: the drobo won’t let it in. So, as you suspected, that leaves the heavy duty option of backup and reformat - which is also the message I am getting from MacOs itself. But backing up 1.6 TB of data doesn’t sound to me like a straightforward (or quick) task ! However, if it has to be done, so be it, but I’ll need to buy more kit. The alternative is to get another drobo anyway (one of the models you mention) and transfer the drives. Drobo Support have now sent me instructions for that, but, as you surmise, there are risks with that too. I mentioned Disk Warrior, which I think is a Mac directory repair tool. I could only try it on the Mac; it almost certainly isn’t a tool for use on the drobo. Nonetheless, is there any potential value in trying that first ? I saw another post on this forum where Disk Warrior did seem to resolve the read-only problem. Another possibility is to move off drobo kit altogether and go for something like Synology - and transfer the drobo data there. Any further views you may have would be much appreciated. Thanks again.

I do monthly full backups & daily incremental on more data than that, it won’t be a 2 minute job, but won’t be that terrible either, it’s a small enough amount to simply park temporarily on an external drive.
If you get another unit (Drobo or other doesn’t really matter, other than a Drobo gives you an option if your old unit dies to read the disk pack from it) setting up a system where one unit backs up to the other regularly is a good idea.

I’ve heard good reports on DiskWarrior, & you’ll find some successes mentioned on here using it, I can’t offer an opinion from experience though, I’m a PC user.

Many thanks once again. This helps me see the way forward.

DiskWarrior has been a ‘go-to’ product for me over the years, but it is only useful now if you have NOT upgraded your Mac file system to APFS. Currently DiskWarrior can only repair and optimize the previous HPF+ file system.

(I am also registered on the Alsoft mailing list for when Apple releases their APFS code to Alsoft so they can develop and release their next DiskWarrior version.)


Thanks for this. My iMac hasn’t been upgraded, so I am going to give DiskWarrior a go. Whether it solves my drobo problem or not, it seems a useful tool to have anyway.