OSX Filesystem Corruption - Need some info :)

Bear with me. I’m a geek on the inside but a grandfather on the outside so I need some very basic questions answered if someone can help!

I have a 2nd Gen 4bay Drobo that I bought years ago. Firewire 800 to a 2009 Mac Pro. All has been well for years. Because of my relative ignorance of being an early adopter I didn’t know oversize format at the beginning to produce one large volume. Rather over the years I added ever larger drives to the current 2tb+2tb+2tb+1tb configuration broken into 4 volumes in OSX Mavericks. All lights are green but in total, the Dashboard shows only about 16% free.

On reboot last night Finder reported that it couldn’t repair the 2nd of the four volumes. It gave the typical “copy everything you can, reformat, and copy back.” The drive is accessible and mounts but is locked to further writes. I’ve done the copy/format/copy back on single drives before but want to make sure I don’t risk the data on my remaining 3 good volumes on the Drobo.

The plot thickens. I tried Disk Warrior 4.4 and it was able to recreate a working directory showing a only a couple bad folders in the corrupt volume BUT it also reported hardware problems so it refused to rewrite the rebuilt directory to the corrupted volume. So, the drobo says the drives are fine but DW says ONE (?) of them is questionable. I’d replace a bad drive but I don’t know which one it is!

So, my only apparent path of attack is to run Disk Warrior to the preview mode, copy the 2tb of data off the bad volume to an external 2tb drive I have.

Then, I’d like to reformat just that bad volume. In the dashboard the “FORMAT” icon says on mouseover that it will reformat the DROBO! Can someone assure me that it will let me simply pick the bad volume and not reformat/delete all the others?

Or, should I use the Disk Utility under OSX to reformat that volume? The FAQ’s say nothing but Dashboard it recommended but then they scare the devil out of you by NOT telling you what you can and can not do with the “format” button.

I feel I’d be better off if the drive had just failed. Then I could have just replaced the drive and let it rebuild and be done with it. Until then I guess I need to jump through these hoops to at least be able to use the drive until the Drobo decides it has failed.

7tb is just too much data for me to backup. The reason its ON the Drobo is that this is better “backup” than none at all. I can’t afford another Drobo to mirror the active one! I’m sure I could lose most of it but I really would rather not.

Can someone answer the two questions about reformatting one volume? (Dashboard vs Disk Utility)?

Thanks for your attention to this epistle. The FAQ’s don’t really seem to address this issue in any place I can find…

First, great detailed explanation of what you are seeing. Saves a lot of time when trying to formulate helpful replies.

I would use Disk Utility to format the suspect volume.

I would agree your Drobo config is inconvenient. I have a 4X3TB Gen2 with a 8TB and 8TB config. I use it exclusively for Time Machine. The ‘overflow’ 8TB volume exists solely so Time Machine won’t fill the physical space.

Thanks for taking the time to reply. So, you are saying that the disk utility format on one volume won’t affect the other volumes.

Out of pure curiosity, do you know what the Dashboard “Format” button really does? I’d expect surely that it would not wipe all volumes but it would be nice if they told you that!

If you select a volume in disk utility you will see an ‘erase’ selection across the top.

If you select a ‘physical drive/disk’ you get an additional option next to erase, ‘partition’.

Drobo recommends formatting your volumes with Disk Utility, but strongly discourages modifying/creating/deleting partitions with Disk Utility.

So, yes, if you reformat a volume with Disk Utility, it just does it on that selected volume, not all the volumes on the Drobo.

I have only used Dashboard to create volumes on initial setup. For all other maintenance (permissions, file system checks), I use Disk Utility.

Thanks for that.

I have to say, I’m really scratching my head. I finally approached the support line and the guy was very courteous but I left still a little confused. Basically he said:

  1. Disk Warrior will sometimes give hardware failure warnings even when there is none. Simple disk latency can set it off.
  2. The Drobo Dashboard “Format” will format all the drives and I lose everything (gulp).
  3. While the Disk Utility will format the individual volume they don’t recommend it at all since there is a likelihood that the other volumes will become unstable because the redundancy stripes will be messed up by the reformat.

His strong recommendation was to buy another drive of some sort, back it all up and reformat the Drobo as one large volume and copy back. While I’ve always wanted to get rid of all these volumes I’ve hesitated not remembering that only about 4.5TB of the 7TB is available for data. The rest is redundancy. So, given the 2tb of HD I have free here, I could buy another drive for a hundred or so bucks and do as he suggests. Still, not sure just what to do so am sleeping on it!

Thanks very much for your input. What do you think about his comments? Your ideas are what I was thinking when I made my initial post.

Perhaps support misunderstood your query?

Do not use any tool but Dashboard to create/modify volumes.

My personal preference is Disk Utility. DiskWarrior is a great tool for ‘local’ disks, but I would shy away from using it or Drive Genius when there is some ‘automagical’ stuff happening in the device. Checking the health of your volume on a regular interval is a best practice.

Erasing the contents of a volume is not the same thing as deleting/re-creating the volume.

Recreating your Drobo as a single volume is a good idea unless you know you need a smaller volume for some other purpose (Time Machine).

Use your new drive to copy your data off, reformat the Drobo, copy the data back, then use the new external for Time Machine.

Understood. The support guy didn’t even want me to reformat the corrupt volume but I suspect it might be OK. I don’t think I’ll be able to “Erase” it since Finder has put a write lock on it but I think it will let me reformat which is probably the only way to repair the corrupted directory blocks. Still, I have a time capsule router for one backup of my boot drive and also use Super Duper to make a bootable backup on a second internal drive on my Mac Pro so all I’m doing here is trying to clean up a data drive that contains mostly photos and various other media. It would be really nice to have it all on one volume for a change. Makes sharing it all over my network much less tedious than having the data spread over 4 volumes!

I’ll need to use Disk Warrier just to recover the couple corrupted folders in its review mode but since it won’t let me rewrite the directory that’s all I can do with it anyway. I can copy the rest off the corrupted volume just using finder since the volume still mounts.

On the other hand, the 4 smaller volumes are handy since a corruption incident only affects one of them most likely. This makes rebuilding less pressing when it does happen. One large volume would seem to be a handicap when and if IT gets corrupted. Then you’re dead in the water until you copy and reformat the whole mess.

Hopefully I’m making some sort of sense here. Anyway, I do appreciate your input and I understand what you’re saying. But, I"m leery of what he had to say about destabilizing things if I reformat with the Disk Utility though it doesn’t make a lot o f sense to me.

hi goosey,
i’m afraid i dont know much about macs, so i’ll just say 2 brief points :slight_smile:

  1. if youre worried a bit about loosing data, and if you can use/get a spare drive to back up your data before you start trying to fix things, then i would do that indeed.

  2. theres nothing wrong with some extra, smaller volumes, than 1 large volume. (i use 2tb volumes, both for compatability, and for putting my eggs in more than one basket) - which in this day and age, im sure it could be misinterpreted for something else :smiley: