diskarbitrarationd consumes 100% CPU for 10 minutes after ejecting a USB drive

Question

Recently I've had problems when ejecting a Seagate SRD0SP0 USB 2.0 hard drive from my Macbook. It has two partitions, one is my Time Machine backup, the other an ExFAT partition for media. There is also a sparse bundle disk image. When ejecting, diskarbitrationd consumes 100% of one CPU for about 10-15 minutes until finally ejecting. Console contains things like... 1/2/13 6:02:32.097 PM fseventsd[67]: could not open <> (No such file or directory) 1/2/13 6:02:32.097 PM fseventsd[67]: log dir: /Volumes/ExFAT/.fseventsd getting new uuid: B0B6D688-5CB1-4236-BA7E-BB90E19D3C10 1/2/13 6:07:58.336 PM fseventsd[67]: Events arrived for /Volumes/DiskImage after an unmount request! Re-initializing. 1/2/13 6:07:58.336 PM fseventsd[67]: creating a dls for /Volumes/DiskImage but it already has one... 1/2/13 6:08:03.755 PM fseventsd[67]: Events arrived for /Volumes/ExFAT after an unmount request! Re-initializing. 1/2/13 6:08:03.755 PM fseventsd[67]: creating a dls for /Volumes/ExFAT but it already has one... 1/2/13 6:08:04.227 PM mds[57]: (Error) LSOF: File '/Volumes/ExFAT' (fd=11) left open on device 16777222 1/2/13 6:15:53.927 PM SystemUIServer[302]: Error getting disk for path /Volumes/Backup: Couldn't stat disk 1/2/13 6:16:08.033 PM SystemUIServer[302]: Error getting disk for path /Volumes/Backup: Couldn't stat disk I've changed the volume names to be more obvious which is which. I've run Disk First Aid on both partitions. This is OS X 10.8.2 and was cleanly installed a few weeks ago. I have no special software running but Sophos An Any ideas what the problem might be or how I might go about diagnosing?

dezzeus · Answer

I have to say that I'm not sure, but to me, the problem with the logged "events" seems to be the indexing of the sparse bundle disk image.

I suppose that "Spotlight" attempt to index both:

The disk image mounted (and indexed) volume, because you probably edit something (perhaps involontary - keep a look with lsof or something similar).
And the directory that contain that disk image, because of the previous point (and the nature of sparse bundle disk images).

And I suppose that the latter may keep updating its index until the first is not completed…

Perhaps Mac OS X tries to defragment the parts of the sparse bundle…

Perhaps (and possibly) it's the Antivirus which is configurated to do something with the mounted volumes… (and which you probably don't really need at all)

The firsts logs let me think of a bad block… perhaps a failing drive ?

Additionally, consider that exFAT is optimized for flash drives, not mechanical hard disks; this can somehow impact the overall performance…

Also I once read (I don't remember where) that Mac OS X's exFAT implementation wasn't a great one; and honestly I did not expect that Apple changed it since its first integration.

My suggested solution – because of the main Spotlight mention in the logs – is to move the disk image file (and any other file that you don't need to index) to a subdirectory and instruct Spotlight's metadata server to not index it nor (if you don't mind) the corresponding mounted volume (you can use the mdutil command line tool); but I'd suggest to not index the exFAT partition at all, except you really need that. But I'll keep an eye on both drive health and Sophos behaviour...

diskarbitrarationd consumes 100% CPU for 10 minutes after ejecting a USB drive

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