Re: [linux-lvm] How to implement live migration of VMs in thinlv after using lvmlockd

[Zhiyong Ye <yezhiyong@bytedance.com>]

Hi Dave,

Thank you for your reply!

Does this mean that there is no way to live migrate VMs when using lvmlockd?

As you describe, the granularity of thinlv's sharing/unsharing is per 
read/write IO, except that lvmlockd reinforces this limitation for the 
lvm activation command.

Is it possible to modify the code of lvmlockd to break this limitation 
and let libvirt/qemu guarantee the mutual exclusivity of each read/write 
IO across hosts when live migration?

Thanks!

Zhiyong

在 11/1/22 10:42 PM, David Teigland 写道:
> On Tue, Nov 01, 2022 at 01:36:17PM +0800, Zhiyong Ye wrote:
>> Hi all,
>>
>> I want to implement live migration of VMs in the lvm + lvmlockd + sanlock
>> environment. There are multiple hosts in the cluster using the same iscsi
>> connection, and the VMs are running on this environment using thinlv
>> volumes. But if want to live migrate the vm, it will be difficult since
>> thinlv which from the same thin pool can only be exclusive active on one
>> host.
>>
>> I found a previous subject that discussed this issue:
>>
>> https://lore.kernel.org/all/20180305165926.GA20527@redhat.com/
> 
> Hi, in that email I tried to point out that the real problem is not the
> locking, but rather the inability of dm-thin to share a thin pool among
> multiple hosts.  The locking restrictions just reflect that technical
> limitation.
> 
> Dave
> 

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