[linux-lvm] Simulating LVM Mirror Failure and recovery

[Eric Brunson]

On 04/16/2009 07:36 AM, Eric Brunson wrote:
> On 04/16/2009 06:54 AM, Alasdair G Kergon wrote:
>> On Thu, Apr 16, 2009 at 07:07:57AM -0500, vu pham wrote:
>>> yogeen honnavar wrote:
>>>> Dear users,
>>>> dd if=/dev/zero of=/dev/vg1/lv1 count=10
>>>> as per the redhat guide this should result in mirror leg failure 
>>>> and any
>>
>> Can you provide the reference - where does it say this?
>>
>> Alasdair
>
> I believe this is the reference.
>
> http://www.redhat.com/docs/en-US/Red_Hat_Enterprise_Linux/5/html/Cluster_Logical_Volume_Manager/mirrorrecover.html 
>
>
> Their example may be in error.
>
>

Upon review, I think it's correct, but worded awkwardly:

    In this example, the primary leg of the mirror |/dev/sda1| fails.
    Any write activity to the mirrored volume causes LVM to detect the
    failed mirror. When this occurs, LVM converts the mirror into a
    single linear volume. In this case, to trigger the conversion, we
    execute a |dd| command

    [root at link-08 ~]#*|dd if=/dev/zero of=/dev/vg/groupfs count=10|*
    10+0 records in
    10+0 records out


I believe the dd is not to cause the failure, it's simply to generate 
write activity to the volume group after the mirror leg has been caused 
to fail through other means not documented.

Anyone else think that's the case?

e.

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