Storage Thin - Dell SAN PowerVault MD3800

[sntms]

Hi,

I have succesfully configured a Proxmox cluster with only 2 nodes at the moment (planning to add 2 more nodes) and I'm experimenting different storage configurations.
I'm using an old setup no longer supported from Dell:

- 2 x Dell R720
- 1 x Dell MD3800 - SAN

The SAN is connected with fibre channel to both nodes of the cluster. I'm able to configure LVM shared volumes and to Live Migrate VM's. The only problem is that I can only configure VM's without Thin Disks allocation.

Is there a way to properly configure this setup in order to have both shared storage and thin disks?
Accordingly to the wiki here https://pve.proxmox.com/wiki/Storage I understood that this in not as easy as I thought.

Looking forward for some advices, thanks for the help!

 

[bbgeek17]

The short answer to your questions is - No. The long answer - No, there is no way to configure shared storage to use LVM Thin allocation.

LVM Thin is not compatible with shared disk access requirements. Proxmox will not allow you to use it that way. If you try to somehow force it in that mode - you will get data corruption.

If your requirement is thin allocation using your existing storage infrastructure, then the only option is to use a proper Clustered File System.
https://en.wikipedia.org/wiki/Clustered_file_system

There are a few options available and you will have to decide which one works best for you. The Kernel/userland management of this file system will run on each PVE node. However its configuration and management will be completely independent of PVE. From Proxmox perspective it will be a "Directory" type storage where QCOWs will be placed. The benefits are: Thin allocation with QCow, HA, Snapshots, relatively reduced complexity.
The drawbacks : having to manage the CFS independent of the Hypervisor. Limited support from PVE official channels for storage related issues.

The second option requires additional infrastructure:
Front-end the block storage that you have today with some sort of NAS that presents CIFS or NFS. The protocols are natively supported by PVE and are easy to configure. Your VMs will utilize QCOW storage format for their disks which gets you native Thin Allocation. The drawbacks are :
- a yet to be quantified hit on performance (FC>nfs/cifs>qcow) which may not be noticeable or matter to you.
- if HA is required - you will need to deploy NAS accordingly
- extra moving pieces

Finally, a 3rd option is to front-end your SAN with a supported ZFS/iSCSI capable server that will allow you to deploy ZFS over iSCSI. Similarly to option #2 you get:
+ Thin Allocation
+ Snapshots
- DIY HA if any
- Performance implications
- extra intermediary pieces

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