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Comment by ArnoldP | Hacker News Reader

I wonder if they limited the drive in software to 314gb and it's just a 500gb drive in reality. I have no idea how actual disks are produced and whether or not it's feasible to make specific platters for each product.

In any case very interesting, I wish there was a decent system w/ SATA for making DIY NAS devices, it seems though each raspi-ish with sata lacks gigabit ethernet, or they are limited to USB speeds.

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>I wonder if they limited the drive in software to 314gb and it's just a 500gb drive in reality.

You're probably getting a 500gb or 320gb drive with a lot of failed blocks that would normally be sold through their 're-certified' channel.

I'd stay away from these. Mechanical drives aren't like CPUs or flash media, where turning down the clock or just ignoring the bad blocks means they'll be fine. If there's an issue with spinning drives it probably means there's a larger mechanical issue that will only get worse or lead to an early failure.

320 GB is a standard size of 2.5" form factor hard drive.

From what I understand these could be 320GB drives that were rejected because they had too many bad sectors, but still had over 314GB of usable storage. Manufacturers usually don't, but they can definitely control in firmware --- down to individual sectors --- how much usable capacity a drive has. A drive that didn't make 320 would likely be cut down to 250. They don't do it more granular than that because it would either mean a proliferation of models of very similar capacities, with the associated complexity of stock-keeping, or they'd have to sell drives where e.g. 320GB would mean a guaranteed minimum and you might get a 321, 325, or 323GB unit. (The early PC hard drives that came with a list of bad sectors physically printed on them were like this --- some would have more, and some would have less, but they'd all be within a few KB of a "nominal" capacity.)

I wonder if they made this one exactly 613,592,315 sectors...

Years ago WD sold a 808.8GB drive which reportedly contained two 500GB platters that had failed QC.

http://www.newegg.com/Product/Product.aspx?Item=9SIA67S23Y89...

It always scares me when buying smaller than normal hard drives in that I am actually just buying drives that have failed QC.

But they passed the 2nd QC check, so all good!

Hope you never buy anything other than the fastest GPU and CPU for a given model :)

I think a lot of Flash-based storage devices still work like this - the exact number of blocks they expose depends on how many defects the particular dies happened to have.

I am not sure if this still done with NAND memory - unit cost is low enough that they seem to just dump the bad examples or worse, off load them to dodgy buyers who make those offbrand novelty flash drives sold on ebay.

Not just hard drives, but CPUs are sold like this as well.

For DIY NAS devices I think you need to spend more ($128 USD) and get something like the APU 2 http://www.pcengines.ch/apu2c4.htm and add more SATA ports with the mini PCI express slots.

I got a banana-pi m3 but the onboard sata is now just a USB bridge :(

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