kern/111967: glabel - label is seemingly not written to disk immediately

[Peter Schuller]

>Number:         111967
>Category:       kern
>Synopsis:       glabel - label is seemingly not written to disk immediately
>Confidential:   no
>Severity:       serious
>Priority:       medium
>Responsible:    freebsd-bugs
>State:          open
>Quarter:        
>Keywords:       
>Date-Required:
>Class:          sw-bug
>Submitter-Id:   current-users
>Arrival-Date:   Fri Apr 20 19:00:09 GMT 2007
>Closed-Date:
>Last-Modified:
>Originator:     Peter Schuller
>Release:        7-CURRENT; also appears on 6.x
>Organization:
N/A
>Environment:
7.0-CURRENT FreeBSD 7.0-CURRENT #0: Tue Apr 17 00:54:35 CEST 2007 
>Description:
The following has now happened to me several times:

(1) glabel any device
(2) crash the machine in one way or another
(3) watch the label be gone on reboot

I was experiencing this several times some time ago when playing with labels and geli on USB drives. I ended up having to label and make sure I perform a clean shutdown and rebooting, before I could ever trust a label. A "sync" has no effect at all. The label can disappear even after extended periods of uptime.

I now had this happen again; I had two SATA drives that I glabel:ed and used in a ZFS pool. A couple of days later I performed a crash test - hit reset during heavy I/O. When the machine came up, one of the labels in the pool was gone. After glabel:ing it again (using the same name) the ZFS pool became healthy again.

In summary I have now seen this happen on at least 7-CURRENT, 6.1-RELEASE or 6.2-RELEASE (not sure which one I had at the time), and with both USB and SATA drives.

The effect can be pretty bad since you can be running for weeks thinking your data is safe, and then the label is blown away. Usually you may be able to just re-lable, but this may not always be the case - especially considering the point of labeling is to not have to keep track of which disk is which.
>How-To-Repeat:

>Fix:

>Release-Note:
>Audit-Trail:
>Unformatted: