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Comment by lucb1e | Hacker News Reader

I don't understand this: 6TB drives are more expensive per gigabyte and they even mention it in their post. They say that they expect the drives to become cheaper over time and that's why they are switching now. Wait, what? Switching now when they are, I quote, "at the top of the curve"[1] does not make sense?

It might be that the physical space reduction compensates for it, but they don't mention that so I don't get it.

[1] https://www.backblaze.com/blog/wp-content/uploads/2014/08/bl...

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My read was they they aren't switching over everything - they are testing new drives, to figure out what reliability looks like.

Once the cost curve costs over, they will then know which vendors drives to go all in on.

Oh, that explains, thanks :)

Yeah, I don't think they replace drives in pods until they fail. Even if they're old 1TB models. The drive costs just outstrip their infrastructure costs by so much that 4 racks of 1TB drives is still cheaper than retrofitting even 1 rack with new 4TB drives.

Yev from Backblaze here -> What we meant by "the top of the curve" was that the price per GB for the 6TB drives is still high, but will decrease greatly as time goes on. The "The Backblaze Cross Under Point" section of the blog will explain it a bit better. We're not quite fully switching over yet, just testing the hardware.

They're testing out 6tb drives early, so when the time comes to fully switch over. They know what drives to get from what manufacturer. They'll also have a better idea when to switch over.

Not just the physical space, but also the power and cooling and serving requirements might tip the balance in favour of a higher upfront cost, but lower lifetime cost.

They mentioned power and that's a flat fee for them, so I didn't mention it.

BrianW from Backblaze here. Exactly. In rough numbers, 1 hard drive always takes the same power to spin up and to cool, regardless of how big of capacity it is. Also, going from 3 TByte drives up to 6 TByte drives means we have half as many hard drives (pods) to deploy every week and so we don't need to hire as many datacenter employees to deploy and maintain pods. Basically we have a little spreadsheet (it isn't complicated, but it has 10 line items on it) that tells us whether a certain price for a hard drive is a good deal or not in the 2 year timeframe, the 3 year timeframe, and the 4 year timeframe.

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