feature request: "LVMthin over iscsi" storage plugin

[alma21]

Hi,

I would like to request/suggest a new integrated PVE Storage plugin: "LVMthin over iscsi". It should work similiar as the zfs over iscsi plugin but instead of zpool/zvols it should use lvm thin pools / thin LVs

some reasons:
- zfs is superior in managing local disks where direct access is granted ... I think (meanwhile) in combination with SANs/LUNs LVM/thin is the better approach
- LVM/thin is more HA cluster/pacemaker friendly
- although ZFS is a first class citizen in ProxmoxVE/Ubuntu not all enterprise distributions support it ... LVM/thin works out of the box on nearly every Linux distribution
- LVM/thin is more lightweight
- LVM/thin is not on par with ZFS but you can add/stack different dm targets together to get similiar features

 

[LnxBil]

LVM thin is not cluster aware and therefore has to be viewed as a kind of a local storage as ZFS. Same with additive dm targets. So most of the reasons are moot in my book. Just using LVM/thin-LVM instead of ZFS in ZFS-over-iscsi is still a viable option, at least technically.

Although I really like ZFS-over-iSCSI, I would suspect that the user base is very small. Most enterprise customers just go with LVM on RAW LUNs and all other have proper storage integration with their own plugin, so none of them would benefit from any ... xxx-over-iscsi plugin.

I can recommend to develop the plugin yourself and try to get it merged upstream or provide it through the storage plugin api.

 

[longer]

I am also not sure if LVM-Thin can be safely shared between different nodes?

Currently if the backend storage support thin-provisioning and discard, then (I think) you are more less having the same features as if its "LVMthin over iscsi".
I mean then you can use iSCSI/FC LUN with shared LVM-thick in the default configuration:
https://pve.proxmox.com/wiki/Migrate_to_Proxmox_VE#Storage_boxes_(SAN/NAS)
Then you can over-provision the exported LUN to PVE

 

[alma21]

LVM thin is not cluster aware and therefore has to be viewed as a kind of a local storage as ZFS

LVM thin is per se not cluster aware ... this is correct .... but the idea is to have e.g. 2 storage/frontend VM "controllers" to your SAN(s) which are running in a dedicated HA active/passive (LVM thin/iscsi target) pacemaker cluster under Proxmox VE .... with such HA-LVM cluster you can use many features of LVM (incl. thinpool) as it would be "local" .... so you get thin provisioning, snapshots ... you can online pvmove / mirror/raid between different SAN vendors / LUNs etc. ... I would say viable options ..... one missing part ... a Proxmox VE Storage LVMthin over iscsi plugin
imho it should also work with zfs but i think there are too many rough edges in such a scenario

 

[LnxBil]

dedicated HA active/passive

Although such a system is tempting, but no enterprise I know does this, everything is active/active and any software solution I came across claims it does that, but does not fullfill all HA requirements and zero data loss. There are also products that claim they can give you active/passive ZFS, so no need for LVM-thin, if the software already supports ZFS. LVM-thin is inferior to ZFS in any aspect but memory consumption and has no advantage in an active/passive setup.

Isn't one of StarWinds products exactly this? I have ZFS-over-iSCSI in my lab and it's great but I never wanted to have LVM-thin, just too old and clumsy in comparison to ZFS. Your milage may vary.

 

[alma21]

active/active is some marketing buzzword used for different things ..... serve one Pool/VG through node/controller1 and another Pool through node/controller2 in above HA setup and you have also active/active ....