And that's a problem with RAID NAS setups. Blocks and Files report that users are experiencing problems adding the latest WD Red NAS drives to RAID arrays, they suspected it is because they are actually shingled magnetic recording drives submarined into the channel.
Alan Brown, a network manager at UCL Mullard Space Science Laboratory, the UK’s largest university-based space research group, told Blocks and Files about his problems adding a new WD Red NAS drive to a RAID array at his home. Although it was sold as a RAID drive, the device “keep getting kicked out of RAID arrays due to errors during resilvering,” he said. Similar issues have been reported at the Synology forums.
Shingled media recording (SMR) disk drives take advantage of disk write tracks being wider than read tracks to partially overlap write tracks and so enable more tracks to be written to a disk platter. This means more data can be stored on a shingled disk than an ordinary drive. However, SMR drives are not intended for random write IO use cases because the write performance is much slower than with a non-SMR drive. Therefore they are not recommended for NAS use cases featuring significant random write workloads. The guys brought all these points to Western Digital’s attention and a spokesperson told us:
“All our WD Red drives are designed meet or exceed the performance requirements and specifications for common small business/home NAS workloads. We work closely with major NAS providers to ensure WD Red HDDs (and SSDs) at all capacities have broad compatibility with host systems. “Currently, Western Digital’s WD Red 2TB-6TB drives are device-managed SMR (DMSMR). WD Red 8TB-14TB drives are CMR-based. “You are correct that we do not specify recording technology in our WD Red HDD documentation. “We strive to make the experience for our NAS customers seamless, and recording technology typically does not impact small business/home NAS-based use cases. In device-managed SMR HDDs, the drive does its internal data management during idle times. In a typical small business/home NAS environment, workloads tend to be bursty in nature, leaving sufficient idle time for garbage collection and other maintenance operations. “In our testing of WD Red drives, we have not found RAID rebuild issues due to SMR technology. “We would be happy to work with customers on experiences they may have, but would need further, detailed information for each individual situation.”
If all that is correct then there is no solution to the problem at hand, other than returning the HDD and replace it with another one. The Western Digital markets WD Red series has been marketed as NAS HDD, and as it seems now, certain revisions will have RAID issues. WD seriously goofed up here in their communication. of course for non-RAID setups, this is not an issue. Remember, the latest WD Red 2TB-6TB WD NAS ready drives seem to use shingled magnetic recording.