People might take hard drives for granted these days. After all, their use of moving parts makes them less suited for mobile devices and their bulky sizes give off an “old school” vibe. Hard disks and their magnetic plates and moving read/write heads, however, still trump Flash NAND technology when it comes to capacity, which is why they are still the go-to for large storage devices like NAS. Unfortunately, picking out a hard drive is harder than you might think, especially when manufacturers themselves aren’t being upfront about the technologies they use.
Network-Attached Storage or NAS devices have become critical for homes and small businesses that need to find a larger and more reliable storage solution. These often use high-capacity, high-speed hard drives in RAIDs (Redundant Array of Independent Disks) for data reliability and integrity. Imagine the surprise, then, of some NAS users when their favorite brand’s NAS drive starts to behave poorly in such a RAID setup.
The culprit, it turns out, is the technology known as Shingled Magnetic Recording or SMR. Unlike Conventional Magnetic Recording (CMR), SMR overlaps tracks a bit when writing data to a platter, creating a structure that resembles the shingles on a roof, hence the name. The compact structure is great for increasing the capacity of a hard drive but it comes at the cost of performance. You can only read and write on SMR drives sequentially because you can’t write to a track underneath another without potentially damaging the data on the upper track.
That makes SMR drives a poor choice for RAIDs where random access I/O is more the norm. Unfortunately, a report from the Blocks and Files site reveals that Western Digital’s Red NAS drive is actually using SMR even if it doesn’t state it in any documentation. WD isn’t the only culprit, though, as both Seagate (UPDATE: see official statement below) as well as Toshiba also later admitted some of their drives marketed for NAS use employ a technique that is known to be bad for NAS use.
None of these three HDD makers find anything wrong with the little white lies. They basically claim that what they explicitly advertise and document is “consistent” with the drives’ performance. NAS users, however, might beg to differ.
UPDATE: A Seagate representative reached out to give this official statement:
“Seagate’s Iron Wolf and Iron Wold Pro HDDs are built for NAS and we confirm that Seagate does not utilize Shingled Magnetic Recording technology (SMR) in any IronWolf or IronWolf Pro drives. We utilize only Conventional Magnetic Recording (CMR) in all IronWolf and IronWolf Pro drives.”
UPDATE 2: A Toshiba spokesperson highlighted the fact that the P300 hard drive is not recommended for NAS use. Instead, the company recommends the N300 for NAS devices.