Thanks to the FreeNAS community, we have uncovered a potential ZFS compatibility issue with some capacities of newer WD Red drives that use Shingled Magnetic Recording (SMR) technology.
Western Digital’s WD Red hard drives are commonly used in FreeNAS Minis due to good affordability and low power/acoustic footprint. They are also a popular choice among FreeNAS community members building systems of up to 8 drives. In general, the WD Reds have a normal workload rating of 180TB/year and are specified to work with NAS and RAID systems with up to 8 drives. Most NAS systems will write their drive capacity less than once per month, and most applications where WD Reds are used will typically write far less than that, which is why they were selected as the companion drive for the FreeNAS Mini.
Previous generation WD Red drives and higher capacity (8TB or greater) models in the current generation drives use CMR (Conventional Magnetic Recording), as do WD Red Pro and all the Enterprise-class drives such as WD Gold and Ultrastar. These CMR drives all perform well and are very reliable under ZFS.
Smaller WD Red drives (2 to 6TB) from their newest generation, released in late 2018, use a different recording technology known as DM-SMR (Device-Managed Shingled Magnetic Recording) . The 2TB, 3TB, 4TB, and 6TB WD Red DM-SMR drives can be identified by the letters “EFAX” in their product code. There are also the previous generation WD Red drives in the same capacities that are CMR drives (identified by “EFRX” in their product codes). The 8TB and larger drives with the “EFAX” code use CMR technology. Realizing this is a little difficult to track, Western Digital has provided a chart to identify all of their drives with DM-SMR.
iXsystems and Western Digital have been working to identify and resolve the ZFS compatibility issue with the WD Red DM-SMR drives. The testing is not yet complete, but at this stage, we can confirm:
Both iXsystems and Western Digital treat data loss as a serious event. We will be doing more work with them to identify and resolve the drive ZFS compatibility issue. Any solution will then be validated with some heavy ZFS workloads with FreeNAS 11.3 and TrueNAS CORE 12.0 before we report back to the community. Follow Western Digital’s blog for more information.
Any existing systems with these drives should have a backup strategy, as should all systems with valuable data. If anyone experiences the IDNF errors with FreeNAS, please contact us and we will advise on how best to handle the situation. Any FreeNAS Mini users will be covered under the standard warranty. There will be more communication when we understand how best to mitigate or resolve the ZFS compatibility issues.
In the meantime, iXsystems will not ship Minis with the impacted WD Red DM-SMR drives. We will instead be using other WD Red drives or WD Red Pro drives. None of the Mini systems available on Amazon use these DM-SMR drives. It is also recommended that the FreeNAS community avoid using these WD Red DM-SMR drives in their own FreeNAS builds until further information is available.
We expect to resume the use of WD Red DM-SMR drives for specific configurations after we have validated a ZFS-compatible firmware version. We will also characterize the performance of these DM-SMR drives for the community. There will always be options for configuring FreeNAS Minis with drives using CMR technology.
If you have any questions about what to use for your next FreeNAS system, please use the community forum or contact iXsystems.