[ClusterLabs] Live migration possible with KSM ?

[Lentes, Bernd]

----- On Mar 30, 2021, at 7:54 PM, hunter86 bg hunter86_bg at yahoo.com wrote:

> Keep in mind that KSM is highly cpu intensive and is most suitable for same type
> of VMs,so similar memory pages will be merged until a change happen (and that
> change is allocated elsewhere).

> In oVirt migration is possible with KSM actively working, so it should work with
> pacemaker.

> I doubt that KSM would be a problem... most probably performance would not be
> optimal.

> Best Regards,
> Strahil Nikolov

>> On Tue, Mar 30, 2021 at 19:47, Andrei Borzenkov
>> <arvidjaar at gmail.com> wrote:
>> On 30.03.2021 18:16, Lentes, Bernd wrote:
>> > Hi,

>>> currently i'm reading "Mastering KVM Virtualization", published by Packt
>> > Publishing, a book i can really recommend.
>>> There are some proposals for tuning guests. One is KSM (kernel samepage
>> > merging), which sounds quite interesting.
>>> Especially in a system with lots of virtual machines with the same OS this could
>> > lead to significant merory saving.
>>> I'd like to test, but i don't know if KSM maybe prevents live migration in a
>> > pacemaker cluster.

>> I do not think pacemaker cares or is aware about KSM. It just tells
>> resource agent to perform migration; what happens is entirely up to
>> resource agent.

>> If you can migrate without pacemaker you can also migrate with pacemaker.

Just to give a feedback.
I configured KSM on both nodes. On one it saves me nearly 20GB RAM.
I checked live migration and it worked.

Bernd
-------------- next part --------------
A non-text attachment was scrubbed...
Name: smime.p7s
Type: application/pkcs7-signature
Size: 2217 bytes
Desc: S/MIME Cryptographic Signature
URL: <https://lists.clusterlabs.org/pipermail/users/attachments/20210331/f1fc1ea7/attachment.p7s>