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News emerged earlier this week that Western Digital was producing NAS hard drives using SMR technology -- which results in slower performance in some types of applications -- without disclosing that fact to customers in marketing materials or specification sheets. After a bit of continued prodding, storage industry sage Chris Mellor secured statements from both Seagate and Toshiba that confirmed that those companies, too, are selling drives using the slow SMR technology without informing their customers. The latter two even use the tech in hard drives destined for desktop PCs.

Given that SMR drives suffer from abysmal random write performance, which is a key type of write pattern that impacts performance in desktop operating systems, the drives will result in noticeably slower performance for PC users.

It's important to understand that there are different methods of recording data to a hard drive, and of the productized methods, shingled magnetic recording (SMR) is by far the slowest. That results in a perceivable difference in performance and even compatibility issues with some types of applications (like RAID). As such, these drives are mainly intended for write-once-read-many (WORM) applications, like archival and cold data storage, and certainly not as boot drives for mainstream PC users.

Due to the complexities of increasing drive density, the industry developed SMR to boost hard drive capacity within the same footprint. The tactic revolves around writing data tracks over one another in a 'shingled' arrangement. The original concept hinged on systems designed top-down from the hardware, software, and file systems, to reduce the performance penalties. However, the complexity and cost of adopting those types of systems (host-managed SMR) prevented the industry from adopting the drives en masse.

As a middle ground, the hard drive industry, which winnowed down to three players due to the brutal economics of producing hard drives in the emerging era of SSDs, developed SMR drives that can work in any normal system (drive-managed SMR). This type of drive is cheaper for HDD vendors to produce, equating to savings that used to be passed down to the customer. But the noticeably poorer performance required vendors to disclose that critical fact to consumers.

Unfortunately, the industry has now shifted to selling these drives in product families that have traditionally consisted of 'normal' models that use the faster conventional magnetic recording (CMR) technique, but without disclosing that fact to consumers.

For WD, that consisted of working the SMR models into its WD Red line of drives, but only the lower-capacity 2TB to 6TB models. Slower SMR drives do make some measure of sense in this type of application, provided the NAS is used for bulk data storage. Still, compatibility issues have cropped up in RAID and ZFS applications that users have attributed to the unique performance characteristics of the drives.

Toshiba tells Block and Files that it is also selling SMR drives without listing them on spec sheets, but does so within its P300 series of desktop drives. Seagate also disclosed that it uses the tech in four models, including its Desktop HDD 5TB, without advertising that fact. However, Seagate, like others, does correctly label several of their archival hard drives as using SMR tech, making the lack of disclosure on mainstream models a bit puzzling.

Boosting HDD capacity is a tough proposition in the razor-thin margin world of hard drive production, and the most promising techniques, which use exotic approaches like lasers or even microwaves, aren't as economical. That stings in an industry where SSDs are fast becoming the de-facto solution due to their speedy performance, so hard drive vendors have retreated further into the 'cheap and deep' storage space. That means focusing on less-expensive and higher-capacity drives, even if it comes at the cost of reduced performance.

Now, we're all for cheaper and deeper storage tech like SMR, but given the comparatively terrible performance in random write workloads (a specification that none of the vendors reveal in their documentation), it goes without saying that this should be clearly indicated to customers on spec sheets and marketing materials so they can decide where, and when, to use the drives.

You can check out our previous article for a deeper look at how SMR technology works.