Bug 274103 - geom_mirror should not use underlying provider with WRITE_PROTECTED flag
Summary: geom_mirror should not use underlying provider with WRITE_PROTECTED flag
Status: Open
Alias: None
Product: Base System
Classification: Unclassified
Component: kern (show other bugs)
Version: Unspecified
Hardware: Any Any
: --- Affects Some People
Assignee: freebsd-geom (Nobody)
URL:
Keywords:
Depends on:
Blocks:
 
Reported: 2023-09-26 11:30 UTC by ant2
Modified: 2023-10-01 18:10 UTC (History)
2 users (show)

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Description ant2 2023-09-26 11:30:42 UTC 
This is a horror story with production server that hanged and did not reboot. This was a rare case that one can't predict and it related to logic inside geom_gmirror so I think  it is actual for all version of FreeBSD.

Background:
There was two SAS HDD: Toshiba and Seagate ST1800MM0129.
Both are GPT partitioned and three UFS paritition are mirrored on each other.

Failure:
There was an error from Seagate disk logged in /var/messages. Error seemed serious. Because of no ability to physically remove Seagate from system there  was a decision do logically detach it from system.
It've been realized by series of command like "gmirror detach". There was a long time of each command. One command hangs, other command seems complete but mirror status stayed the same. Because of this there was a decision to reboot.

After reboot system hangs during geom_mirror initialization.
Also tried a FreeBSD 13-STABLE USB-stick but result was the same.

Cause:
(this is mostly reconstruction because there was no time to explore problem meaningfully)

After reboot (reinitialization?) Seagate ST1800MM0129 goes to read-only mode because of internal hardware failure. It appear in camcontrol(?) with flag MEDIUM: WRITE_PROTECTED. Geom_mirror unexpect this case and attach it as usual as part of a mirror. But with the first attempt to write to it hangs.


Summary:

geom_mirror must check each mirror component for WRITE_PROTECTED flag and do not attach such a component to a mirror (at least during initialization)

P.S. Solution for people in this situation: use Seagate SeaChest tools for FreeBSD to engage self-wiping process on failure disk. Disk will become clean and geom_mirror will initialize successfully.