Re: LVM support in Ceph Pacific

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Hi,

Thanks for your answers Janne Johansson,
"I'm sure you can if you do it even more manually with ceph-volume, but there should seldom be a need to"
Why do you think "there should seldom be a need to" ?

"Yes, upgrades do not contain LVM management, as far as I have ever seen."
But there will be problems if later one existent OSD must be totally recreated, won't it ?

Best Regards

-----Message d'origine-----
De : Janne Johansson <icepic.dz@xxxxxxxxx> 
Envoyé : mercredi 10 novembre 2021 15:38
À : MERZOUKI, HAMID <hamid.merzouki@xxxxxxxx>
Cc : Ceph Users <ceph-users@xxxxxxx>; Moullé, Alain <alain.moulle@xxxxxxxx>; RIBEIRO, ADRIEN <adrien.ribeiro@xxxxxxxx>
Objet : Re:  LVM support in Ceph Pacific

Caution! External email. Do not open attachments or click links, unless this email comes from a known sender and you know the content is safe.

Den ons 10 nov. 2021 kl 11:27 skrev MERZOUKI, HAMID <hamid.merzouki@xxxxxxxx>:
>
> Hello everybody,
>
> I have a misunderstanding about LVM configuration for OSD devices:
>
> In the pacific documentation cephadm/install (and it was already written in octopus documentation in section DEPLOY OSDS), it is written :
> "The device must not have any LVM state"
> (https://eur01.safelinks.protection.outlook.com/?url=https%3A%2F%2Fdoc
> s.ceph.com%2Fen%2Fpacific%2Fcephadm%2Fservices%2Fosd%2F%23listing-stor
> age-devices&amp;data=04%7C01%7Chamid.merzouki%40atos.net%7C1e593a9838a
> d43928d4e08d9a457aa37%7C33440fc6b7c7412cbb730e70b0198d5a%7C0%7C0%7C637
> 721518745976530%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2
> luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C1000&amp;sdata=knp7V%2FB8xHq2nD
> Iki13BRJSntDmI1axaZnRLMuHCmU4%3D&amp;reserved=0)

I think this mostly means "It should be empty, and not have a previous LVM configuration"

> whereas there are lots of reference to LVM configuration in other sections, such as in release notes : Pacific - Ceph Documentation or in ceph-volume - Ceph Documentation :
> "NEW DEPLOYMENTS" 
> (https://eur01.safelinks.protection.outlook.com/?url=https%3A%2F%2Fdoc
> s.ceph.com%2Fen%2Fpacific%2Fceph-volume%2Findex.html%23new-deployments
> &amp;data=04%7C01%7Chamid.merzouki%40atos.net%7C1e593a9838ad43928d4e08
> d9a457aa37%7C33440fc6b7c7412cbb730e70b0198d5a%7C0%7C0%7C63772151874597
> 6530%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBT
> iI6Ik1haWwiLCJXVCI6Mn0%3D%7C1000&amp;sdata=m9DqoORI63Me%2FEO1d8XYADM89
> i2gpOikNH30DqHR2Gw%3D&amp;reserved=0)
> For new deployments, LVM is recommended, it can use any logical volume 
> as input for data OSDs, or it can setup a minimal/naive logical volume 
> from a device

..and the many mentions of LVM is because the tools will happily default to making a new LVM setup for you on the clean disks you supply.
If there already is LVM on it, the installation needs to take many different situations into consideration, compared to "the disk need to be clean and without previous LVM on it", in which case it can just pvcreate and so on from a clean start.


> So I'm not sure to understand and have two questions:
>
> 1/ Is it possible or not to deploy a Ceph Pacific configuration upon a LVM configuration for OSDs or is it not supported or is it just a problem linked to the use of ceph-adm instead of ceph-ansible ?

I'm sure you can if you do it even more manually with ceph-volume, but there should seldom be a need to. As for if the scripts and tools will allow you to specify such a config I don't know.

> 2/ Is it possible to migrate a Ceph Octopus configuration installed (thks to ceph-ansible) upon LVM configuration for OSDs towards a Ceph Pacific configuration without changing anything around LVM configuration ?

Yes, upgrades do not contain LVM management, as far as I have ever seen.

--
May the most significant bit of your life be positive.
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