gmirror forget question - why forget gm0 instead of ad4?

Pawel Jakub Dawidek pjd at
Sat Dec 3 17:00:07 PST 2005

On Sat, Dec 03, 2005 at 04:00:40PM -0800, M. Royce wrote:
+> I want to be sure I understand how to replace a drive if it fails now that I have gmirror working. I don't understand the forget command.
+> I saw this in comments section of Ralf's web page about gmirror:
+> --------
+> If a drive fails (eg. drive /dev/ad4):
+> # gmirror forget gm0
+> # shutdown -h
+> replace the drive with a fresh one
+> # gmirror insert gm0 /dev/ad4
+> And it should start synchronizing if autosynchronization is turned on.
+> --------
+> Why do you forget gm0? I would think if ad4 failed I'd "forget /dev/ad4".
+> would really appreciate a brief explanation.

If a drive fails or is not detected, gmirror doesn't know if it was ad4,
da0, da0s1a or anything else, because it discovers components based on
their metadata, not names. By doing 'gmirror forget' you say: "forget
about missing components". Without forgetting missing components you
can't run specific actions, which need to be notes in metadata of all

Pawel Jakub Dawidek             
pjd at                 
FreeBSD committer                         Am I Evil? Yes, I Am!
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