While accessing a drive with high error rates (as, for example, here for opensuse) in FreeBSD, the system eventually disconnects the drive and it disappears from /dev. This makes it impossible to run ddrescue or testdrive in any reasonable fashion.


With FreeBSD 9+ the camcontrol utility can be used to control if either a SATA or a SCSI drive is disconnected, or not, in such circumstances:

camcontrol negotiate /dev/<dev> -D disable

Use gmountver; configure it (gmountver create /dev/adaX) and use ddrescue on /dev/adaX.mountver. The mountver device will stay there while adaX`` disappears, and all the disk IO operations will get retried after it reappears.

  • nice! that'll go into my toolbox. – Richard Sitze Jan 28 '15 at 17:04

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