SMR in disk drives: PC vendors also need to be transparent

Western Digital late last week issued a statement in response to the revelation of the company’s undocumented use of SMR (Shingled Magnetic Media recording) in 2TB and 6TB WD Red NAS drives.

Toshiba and Seagate confirmed to Blocks & Files that there is undocumented use of SMR technology in some of their drives. We think it is now time for the PC vendors to come clean.

Desktop and laptop system makers need to be explicit in data sheets and marketing literature when their disk drives use SMR. This will prevent avoidable mishaps of the WD Red NAS variety.

A senior industry source, who declined to be named, told us: “It’s actually not surprising that WD and Seagate offered to OEM out SMR HDDs for desktops – after all, they are cheaper per TB. And sadly, it is also not surprising that the desktop vendors such as Dell and HP integrated them into their machine without ‘telling’ their customers, the end-user consumer (and/or the business desktop buyer, usually a procurement agent)… So, I think the fault is spread around the supply chain – not just the HDD manufacturers.”

SMR is cheaper

In its statement (full text below), WD explains that certain sub-8TB WD Red SMR drive users could experience problems, and also that it uses conventional magnetic recording (CMR) technology in 8TB-14TB WD Red NAS drives.

So why did WD use SMR drives for the sub-8TB capacity points? Very simply, with fewer platters and read and write heads, SMR is a cheaper way to deliver the same capacity as CMR.

WD uses SMR in its 1TB, 2TB, 3TB, 4TB and 6TB Red drives and conventional recording in its 8TB, 10TB, 12TB and 14TB Red drives. We see here a split product line using with each half using different disk recording technology underneath one brand.

And why WD did not use SMR in the 8TB and abovedrives if it could deliver “an optimal performance experience for users”.

WD said in its statement: “In our testing of WD Red drives, we have not found RAID rebuild issues due to drive-managed SMR technology.”

However, users on the Reddit, Synology and smartmontools forums did find problems; for example with ZFS RAID set enlargements and with FreeNAS.

Alan Brown, a network manager at UCL Mullard Space Science Laboratory, who alerted us to the SMR issue, said: “These drives are not fit for purpose. In this case because they have a relatively provable and repeatable firmware bug which result in them throwing hard errors, but in more general purposes because SMR drives marketed as NAS/RAID drives have such appalling and variable throughput that they are unusable.”

“Even the people using Seagate SMR drives are reporting 10 second pauses in writes at times and those who had reasonable performance with SMR-from-start arrays have confirmed that resilvering a replacement drive in has turned out to be a major issue which they didn’t fully appreciate until they actually tried it.”

Western Digital statement

Shingled magnetic recording (SMR) is a hard drive technology that efficiently increases areal density and capacity for users managing increasing amounts of data, thus lowering users’ TCO. There are both device-managed and host-managed types, each for different use cases.

All our WD Red drives are designed to meet or exceed the performance requirements and specifications for common and intended small business/home NAS workloads. WD Red capacities 2TB-6TB currently employ device-managed shingled magnetic recording (DMSMR) to maximize areal density and capacity. WD Red 8-14TB drives use conventional magnetic recording (CMR). DMSMR should not be confused with host-managed SMR (HMSMR), which is designed for data center applications having respective workload requirements and host integration.

DMSMR is designed to manage intelligent data placement within the drive, rather than relying on the host, thus enabling a seamless integration for end users. The data intensity of typical small business/home NAS workloads is intermittent, leaving sufficient idle time for DMSMR drives to perform background data management tasks as needed and continue an optimal performance experience for users.

WD Red drives are designed and tested for an annualized workload rate up to 180TB. Western Digital has seen reports of WD Red use in workloads far exceeding our specs and recommendations. Should users’ use cases exceed intended workloads, we recommend WD Red Pro or Ultrastar data center drives.

Western Digital works extensively with customers and the NAS vendor and partner communities to continually optimize our technology and products for common uses cases. In collaboration with major NAS providers, we work to ensure WD Red HDDs (and SSDs) at all capacities are compatible with a broad set of host systems. In our testing of WD Red drives, we have not found RAID rebuild issues due to DMSMR technology.

Our customers’ experience is important to us. We will continue listening to and collaborating with the broad customer and partner communities to innovate technologies that enable better experiences with, more efficient management of and faster decisions from data.

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