Different hard drives with the same type designation

c’t reader Matthias S. is a conscientious person: Before disposing of IT equipment, he deletes data so thoroughly that it is guaranteed not to be recoverable. He unscrews hard drives to bend the magnetic disks, only then do they come to the recycling yard.

But he was amazed after opening two supposedly identical drives from Western Digital (WD). Despite the identical type designation, they had different contents: One had three discs, the other only two.

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Both drives, each with a 2 TB capacity, were named WD20EZRZ-00Z5HB0, but according to the sticker, one was produced in Thailand on October 3rd, 2015, the other just a few days later, on October 12th, 2015 in Malaysia.

A hard drive with three disks should require a little more power than one with two disks. We would therefore have liked to take a few measurements to find differences between these two “same” hard drives. However, we could no longer use the specimens from S. Searches on eBay & Co. brought up some used WD20EZRZ from Thailand, but not a single one from Malaysia. A new one, which was advertised with a Malaysia photo, also turned out to be a Thailand plate after the purchase.

In response to our request, Western Digital only said that “both products meet the specified technical specifications equally. Different components can be installed on hard drives with the same model number.” The company was able to confirm that both cases were legitimate WD drives.

We only received details from industry experts via detours. The standard production location for mass production is therefore Thailand, whereas special orders tend to be processed in Malaysia – for example, when you need a few hundred thousand pieces of a certain type of hard drive. But hard disks are also produced in stockpiles and later adjusted by firmware depending on current requirements. In the price-sensitive desktop PC market, the only thing that matters is that the capacity is right.

So it could happen that a hard drive design with three disks that was at least two years older received the same sticker as a current one with two disks. The production date on the sticker has little to do with the actual time the hardware was manufactured; it is the date on which this hardware was finalized with the appropriate firmware for this model.

Same model number, different content: there were two discs in the left WD Blue, and three in the right.

According to our information, the more recent two-pane design should already work with panes of glass (platters), but according to our reader, it could bend all five panes – glass would have splintered. So maybe a different design was used. If the WD Blue with 2 TByte is still available with the same type designation in a few years, the content could be changed again: 2 TByte now fit on a single disk.

Something similar is currently happening with the largest available hard drives from Seagate, albeit the other way around: The 16 TB NAS hard drives should contain the same hardware as the 18 TB model, i.e. nine 2 TB disks and 18 read / write Heads. In the 16 TB model, however, two of the heads are deactivated.

According to the information, this saves a few percent of the manufacturing costs due to the higher number of pieces for the same parts. Our measurements with these two Ironwolf hard drives show a slightly higher energy requirement for the larger model, and its speed is also a few percent higher. That was to be expected; in our opinion, this type of cost optimization is not reprehensible. We do not know whether other manufacturers are also doing this; We are happy to receive information about this anonymously via our secure mailbox.

In c’t 6/2021 we would like to make it easier for you to get started with the smart home: We provide practical tips and purchase advice for more security, comfort and efficiency in the intelligent home. If you have your finances under control and want to use home banking for this, you should consult issue 6: In it, we tested six programs for home banking, paying particular attention to data protection. We will also show you how you can cleanly separate your personal phone calls and data from your work in the home office. We are testing GPS trackers for e-bikes, compact document scanners for more order in the office and the first e-car with Android. The school cloud of the Hasso Plattner Institute (HPI) recently revealed a huge security breach. Fortunately, the hole in the platform was closed after our advice. You can read about this and much more in issue 6/2021, which will be published in Heise shop and is available at the well-stocked magazine kiosk.


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