[linux-lvm] Does LVM always do 'dm suspend' when lvcreating a thin snapshot?

[linux-lvm] Does LVM always do 'dm suspend' when lvcreating a thin snapshot?

[Mike McCracken]

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 When creating a thin snapshot of a thin volume, does LVM always freeze the
FS?

I see when I run lvcreate with -vvv that it sends the 'dm suspend' message
to the origin lv, but on looking at the code I wasn't quite able to
convince myself that it will always do that, or under what circumstances it
won't.

Thanks,
-mike

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Re: [linux-lvm] Does LVM always do 'dm suspend' when lvcreating a thin snapshot?

[Zdenek Kabelac]

Dne 4.9.2015 v 00:04 Mike McCracken napsal(a):
> When creating a thin snapshot of a thin volume, does LVM always freeze the FS?
>
> I see when I run lvcreate with -vvv that it sends the 'dm suspend' message to
> the origin lv, but on looking at the code I wasn't quite able to convince
> myself that it will always do that, or under what circumstances it won't.
>

Hi

Yes - suspend of thin's snapshot origin is always enforced
as you normally want snapshot FS to be in consistent state.

Zdenek

Re: [linux-lvm] Does LVM always do 'dm suspend' when lvcreating a thin snapshot?

[Mike McCracken]

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OK, thanks for confirming!
I'd like to help improve the documentation about this - did I miss a place
where it was mentioned explicitly? If not, where would a discussion of FS
suspending fit? I'm happy to contribute a patch.


On Fri, Sep 4, 2015 at 4:05 AM, Zdenek Kabelac <zkabelac@redhat.com> wrote:

> Dne 4.9.2015 v 00:04 Mike McCracken napsal(a):
>
>> When creating a thin snapshot of a thin volume, does LVM always freeze
>> the FS?
>>
>> I see when I run lvcreate with -vvv that it sends the 'dm suspend'
>> message to
>> the origin lv, but on looking at the code I wasn't quite able to convince
>> myself that it will always do that, or under what circumstances it won't.
>>
>>
> Hi
>
> Yes - suspend of thin's snapshot origin is always enforced
> as you normally want snapshot FS to be in consistent state.
>
> Zdenek
>
> _______________________________________________
> linux-lvm mailing list
> linux-lvm@redhat.com
> https://www.redhat.com/mailman/listinfo/linux-lvm
> read the LVM HOW-TO at http://tldp.org/HOWTO/LVM-HOWTO/
>

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