kern/121481: [gmirror] data rot on disk with gmirror

[Dan Naumov]

The following reply was made to PR kern/121481; it has been noted by GNATS.

From: Dan Naumov <dan.naumov at gmail.com>
To: "Steiner, Bernard" <Bernard.Steiner at lahmeyer.de>
Cc: bug-followup at freebsd.org
Subject: Re: kern/121481: [gmirror] data rot on disk with gmirror
Date: Mon, 13 Jul 2009 12:16:33 +0300

 On Mon, Jul 13, 2009 at 11:50 AM, Steiner,
 Bernard<Bernard.Steiner at lahmeyer.de> wrote:
 >> [checksumming utilities]
 >
 > Please explain how to do that on both sides of a gmirror.
 > AFAIK, gmirror can be configured in the following ways:
 > (1) always read from "primary" disk => cannot check secondary
 > (2) round robin or load => read cannot be reliably reproduced
 >
 > Correct me if I am wrong, but this does not seem like a solution
 > to my problem.
 
 You have several options:
 
 Option 1 (this has the benefit of working with all balance algorithms):
 Take disc2 offline, run checksum check (so that checks are done against disc1)
 Take disc2 online, take disc1 offline, run checksum check
 
 Option 2 (for "prefer" algorithm):
 Assuming disk1 is the promoted disk, run checksum check
 Promote disk2, run checksum check
 Promote disk1 to return to original state
 
 - Sincerely,
 Dan Naumov