tl;dr version: An external disk wouldn't mount; I panicked and tried to fix it, then I just gave up and it fixed itself – specifically, the fsck_hfs daemon fixed it for me.
Yesterday, I rebooted my the Mac mini in my office into Windows to play some games, then when I rebooted back into OS X, my Drobo wouldn't mount.
The status lights on it were all normal, and the Drobo Dashboard (which coincidentally I think failed with ‘missing components' necessitating reinstalling) reported it was healthy too, but while the drive showed in System Information and in the Disk Utility tree, if I tried to mount it it just reported that it couldn't, and suggested that I should try to repair it. Install alexa app on mac.
I was a little nervous of doing this since a Drobo uses an unusual disk structure, but its own support documents say you should indeed try repairing the disk if it fails to mount. (It's not actually surprising, since the Drobo's unusual system should be entirely hidden from the Mac; so far as the Mac is concerned, it should be just like any other disk.)
Connected the external HD to my Mac but it won't mount. I tried mounting with `diskutil mount /dev/pathToDisk` and `diskutil mount readOnly /dev/pathToDisk` but it won't mount. The disk is formatted in the Mac OS Extended (Journaled) format (HFS+). I downloaded WD Drive Utilities software to check the HD and it passed WD checks. If you don't know where your Google drive is mounted, use df or mount command as shown below. $ df -h Filesystem Size Used Avail Use% Mounted on udev 968M 0 968M 0% /dev tmpfs 200M 1.6M 198M 1% /run /dev/sda1 20G 7.5G 12G 41% / tmpfs 997M 0 997M 0% /dev/shm tmpfs 5.0M 4.0K 5.0M 1% /run/lock tmpfs 997M 0 997M 0% /sys/fs/cgroup tmpfs 200M 40K.
From this MacWorld article, sometimes a drive can be 'connected' and visible in DiskUtility (not Finder), but not mounted. If that's the case, then you may be able to select the volume in DiskUtility and click the Mount button in the top toolbar, in order to successfully connect it systemwide. When your SD is severely damaged, it will reach to an extent where it can't even mount a file system. When you format an SD card it means mounting a new file system that tracks the storage on your SD card.
Disk Utility, however, reported that the disk was unrepairable. Now, I tried connecting it using USB 2.0 (rather than FireWire 800), and connecting it to another Mac, but still, no dice. I was beginning to resign myself to buying Disk Warrior to laboriously reconstruct the directory structures, but I wasn't quite done troubleshooting yet.
I was a little nervous of doing this since a Drobo uses an unusual disk structure, but its own support documents say you should indeed try repairing the disk if it fails to mount. (It's not actually surprising, since the Drobo's unusual system should be entirely hidden from the Mac; so far as the Mac is concerned, it should be just like any other disk.)
Connected the external HD to my Mac but it won't mount. I tried mounting with `diskutil mount /dev/pathToDisk` and `diskutil mount readOnly /dev/pathToDisk` but it won't mount. The disk is formatted in the Mac OS Extended (Journaled) format (HFS+). I downloaded WD Drive Utilities software to check the HD and it passed WD checks. If you don't know where your Google drive is mounted, use df or mount command as shown below. $ df -h Filesystem Size Used Avail Use% Mounted on udev 968M 0 968M 0% /dev tmpfs 200M 1.6M 198M 1% /run /dev/sda1 20G 7.5G 12G 41% / tmpfs 997M 0 997M 0% /dev/shm tmpfs 5.0M 4.0K 5.0M 1% /run/lock tmpfs 997M 0 997M 0% /sys/fs/cgroup tmpfs 200M 40K.
From this MacWorld article, sometimes a drive can be 'connected' and visible in DiskUtility (not Finder), but not mounted. If that's the case, then you may be able to select the volume in DiskUtility and click the Mount button in the top toolbar, in order to successfully connect it systemwide. When your SD is severely damaged, it will reach to an extent where it can't even mount a file system. When you format an SD card it means mounting a new file system that tracks the storage on your SD card.
Disk Utility, however, reported that the disk was unrepairable. Now, I tried connecting it using USB 2.0 (rather than FireWire 800), and connecting it to another Mac, but still, no dice. I was beginning to resign myself to buying Disk Warrior to laboriously reconstruct the directory structures, but I wasn't quite done troubleshooting yet.
For many users, the easiest way to unmount a drive in Mac is to either just drag a volume into the Trash, use the eject keys, disconnect the drive, or use one of the force eject methods. Along the same lines, if you want to remount a drive you can usually just physically unplug the drive and plug it back again.
My next step was to connect it to yet another Mac, and now I got a faint glimmer of hope. This was my wife's MacBook Air, which is still running OS X 10.9; both my Macs had been upgraded to 10.10. Clicking on iStat Menus, I saw that the fsck_hfs process was running, taking up a lot of the CPU. This is a background process that checks and repairs disks, so with nothing to lose — and knowing that a Drobo support document I read earlier said that if fsck is running, let it complete — I just left it and went to watch telly.
I came back a couple of hours later, and boom; the Drobo was mounted on the desktop of my wife's Mac. Now, one detail I omitted earlier was I had noticed that when the Drobo was connected to either of my Yosemite Macs, a process called diskarbitrationd grabbed a whole chunk of the CPU. Googling it suggested it's a process just concerned with mounting disks, so I had thought it was getting stuck because it couldn't mount the Drobo. I can't find information to suggest diskarbitrationd is a successor to or incorporates the repair elements of fsck, but it's possible that had I just left the Drobo connected to the Mac mini when I first noticed the problem that it would have repaired itself there too. I'm a little annoyed that the Mac apparently had the ability to repair the disk, but loading Disk Utility and clicking Repair – the obvious troubleshooting process – failed with no hint that an invisible, background process was actually capable of doing it, not least because if you know less than I do, you'd just assume that your data was gone, and either start a lengthy restore process or start spending money on new disks.
(The data on the Drobo – mostly our iTunes Library – was backed up, online, to Livedrive, but the idea of downloading 4TB data, even on a fibre connection, wasn't one to fill me with delight.)
Can't Mount Disk Mac
I'm pretty paranoid about backup and data security, but this episode was a reminder that however you protect your data it's never absolutely safe; all you're doing is reducing the risk. The Drobo system allows for a single disk (or, depending on your configuration, two disks) to fail mechanically without losing any data – just pop out the duff disk and slot in a new one, something I've done in the past – but as I was reminded even this doesn't ensure the data is secure, since it only protects against one particular (albeit major) source of data loss.
Usb Drive Won't Mount
It's important to point out that I believe the Drobo system itself was entirely blameless in all of this; I think the fault was one that could have affected a simple single-disk USB drive, and would have been fixed in the same way.
