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Comment by jonatron | Hacker News Reader

https://www.backblaze.com/blog/hard-drive-cost-per-gigabyte/ Has some sad looking graphs.

We are now below $.02 per gigabyte, at $.014-ish at single-unit prices for CMR drives, more or less tracking linearly that last leg of the curve. My guess is that there is a lot of price elasticity in hard disk drives (and that margins aren't as thin as we could hope - which is good, because it allows more R&D spending).

Those aren't that sad looking. You can't go down 4 cents/gb when you're at 4 cents/gb. If you look at the halving period, it's pretty stable at 4-6 years.

Sure you can. Just go to 4 cents per TB.

Yea spinning rust has been plateauing for anything other than SMR disks. A large part of that is that CMR (the old style) just isn't scaling anymore, even though it has much better performance and characteristics than SMR. Combine that with the fact that flash storage has been considerably increasing in density and speed (spinning rust disks haven't really increased in performance either) there's probably not as much investment happening in improving the spinning rust stuff the same way as it used to be. Flash still isn't quite at the same level of cost per storage but it's definitely starting to approach it and will very likely surpass it in the future.

Both seagate and WD are in late stages of developing new platforms that will double the density, with 50TB disks expected around 2025-6.

I'm curious what the performance characteristics will look like. Will they behave more like SMR where they don't work very well in RAID or ZFS due to needing to wipe large portions at a time, or will they be more like CMR where you can reliably do a sector at a time. I really hope it's more like CMR because otherwise the storage just won't really cut it at sizes as small as 50TB by then. With Flash disks being available (though at insane prices) at 100TB right now I'm not convinced there's going to be much of a market with the price/storage and performance stagnation that's been going on.

https://nimbusdata.com/products/exadrive/pricing/ # for the 50-100TB disks, low volumes but available now if you have no budget limits.

One of the big problems is the difference between the capacity curve and the access speed curve. The 22TB HDDs are 22x bigger than the 1TB drives of years ago; but they are no where near 22x faster. Speeds have increased to be sure, but they are in the range of 2x to 3x faster than old drives.

This means that the total time needed to read and/or write all the data on a given drive continues to increase. This is very important for things like backup or RAID rebuilds. Reading 50TB from a drive with 300 MB/s speed will take almost 50 hours.

Also, some might think that this problem somehow goes away if you just move to SSDs; but it does not. The speeds are an order of magnitude faster, but the curves are very similar. A 4TB SSD is not 4x faster than a 1TB SSD.

Isn't this partially solved from the software side though?

It is common in my work to see read replicas of 2-3. Sometimes those replicas are split up into smaller "shards" across multiple disks even further.

Restoring might be pulling from 10 different disks at the same time.

Do they account for inflation?

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