Risk of data corruption with iSCSI and ZFS over iSCSI

[lancer8921]

I'm planning on creating a Proxmox environment and I want to use iSCSI LUNs for VM storage. I read through some of the documentation, but I can't find any mentions of using a clustered filesystem (like GFS2 or another) on the iSCSI LUNs. In VMware vSphere whenever you create an iSCSI datastore you create a VMFS clustered filesystem on top of it. This is so that multiple hypervisor hosts can read/write the same filesystem simultaneously without causing data corruption.

Also, I'm confused over using ZFS for iSCSI. I haven't used ZFS much, but from what I'm aware ZFS is a local filesystem, it doesn't have locking protections when multiple Proxmox nodes try to write to the same file at the same time.

I'm not sure how often this is an issue, but I presume data corruption can happen, so I want to be sure.

 

[UdoB]

You post doesn't contain a question!

ZFS-over-iSCSI is documented here: https://pve.proxmox.com/pve-docs/pve-admin-guide.html#storage_zfs

The problem in 2025 is that the main target (TrueNAS) is actively switching to Linux (to SCALE) and the required plugins (on both ends) are possibly not available, not compatible, not finished or not stable - and (in this state) definitely not officially supported. Note that I write this without hard evidence and current references.

Basically... I'll keep on dreaming...

The officially supported storage types are here: https://pve.proxmox.com/pve-docs/pve-admin-guide.html#_storage_types

 

[bbgeek17]

Also, I'm confused over using ZFS for iSCSI. I haven't used ZFS much, but from what I'm aware ZFS is a local filesystem, it doesn't have locking protections when multiple Proxmox nodes try to write to the same file at the same time.

You are correct about the ZFS being none-cluster-aware. What you are missing - the iSCSI disk (which is backed by ZFS volume) is only assigned to one host/VM at a time. As such, there is no concurrent read or write to it.

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Blockbridge : Ultra low latency all-NVME shared storage for Proxmox - https://www.blockbridge.com/proxmox

 

[alexskysilk]

but from what I'm aware ZFS is a local filesystem

Yes, but not exclusively. the ZFS FILE system is not, but zfs can export zvols (block devices) which are no different then any other block device for the purposes of cluster operations. when use as zfs over iscsi, iscsi just facilitates the transport of zvols, and the cluster manages contention.