vSphere ESX-OSData Evolution: VMFS-L/VFFS to VMFSOS in vSphere 8.0
During my recent interaction with a customer, I came across some noteworthy partitioning alterations, particularly in versions 7.x and beyond, along with their associated naming conventions. This inspired me to consider sharing this valuable information through a blog post to enlighten a broader audience.
You may already be aware about the storage partition modifications introduced in vSphere 7.0 for our ESXi storage partitioning. You can find more details on this topic by visiting esxi-system-storage-changes.
ESX-OSDATA serves as a centralized repository for accommodating supplementary modules and combines various storage components, including the legacy /scratch partition, the locker partition for VMware Tools, and core dump destinations. For a detailed explanation of the storage partition layout and the factors governing partition sizes, please refer to the following link: ESXi System Storage
As per any 7.x version of ESXi, the OSDATA partition would have the filesystem type as VMFS-L which is shown in the below:
However, in situations where our boot device or the storage drive housing the OSDATA is an SSD or NVMe, even if the drive is labeled as “flash” (considering it’s not actually a flash storage device), the OSDATA filesystem will be referred to as the Virtual Flash File System (VFFS).
Consequently, the disk supporting the ESX-OSDATA volume will appear in the Virtual Flash resources section in vCenter. It’s important to note that this disk is associated with the ESX-OSData volume and does not belong to the Virtual Flash resource pool.
This situation can sometimes lead to confusion, as observed with a customer who utilized NetApp local storage, which was not flash storage but was labeled as such by the storage vendor. Out of curiosity, I replicated this scenario in my home lab by marking the drive as “flash” from vCenter. The procedure for performing this action is well-documented in the following resource: Mark Storage Devices as Flash
Post which I updated my ESXi host to one of the newer 7.x patch release version to witness the re-partitioning in action.
Right after the ESXi was rebooted after the patch update was complete, we found the OSDATA partition is updated to VFFS instead of VMFS-L.
Remarkably, as mentioned earlier, while this partition appears within the virtual flash resource management in vCenter, it is not part of the virtual flash resource pool. We observe a similar situation here, where the eligibility section says “Other partitions exist”.
After conducting some research, I discovered that VMware has introduced a new file system called “VMFSOS” with the release of vSphere 8.0U1. This file system is designed specifically for managing the ESX-OSDATA system partition. Notably, this partition remains consistent whether the underlying storage drives are flash-based or non-flash-based.
For further details, you can review the release notes available at the following link: VMware ESXi 8.0 Update 1 Release Notes
In case of ESXi where drive is non-flash,
In case of ESXi where drive is marked as flash,
I hope you find this helpful.
I am grateful for your time and curiosity in exploring this topic. Your engagement fuels the passion for sharing tech insights. Thank you!
