Disk capacities

Larger drives in the 20-40Tbyte range have much closer ratios.

Which suggest they are approaching the limits of the technology. At THAT point.

So, why not a wider variety at lower capacities where, one assumes, they have more "wiggle room" in their offerings??

Typically there's a certain number of bits you can store per platter. eg let's say it's 1T per side.

One read head on one platter gets you 1T Two read heads on both sides of one platter gets you 2T Two platters with four heads gets you 4T Four platters with eight heads gets you 8T

etc etc.

It's not worth retooling for a new generation for only a minor bump to 1.1T per platter, so these models hang around until somebody can manage 1.5T per platter, then we get 1.5T/3T/6T/12T. Then the next bump is to 2T per platter so 2T/4T/8T/16T. Rinse and repeat.

Apart from the largest sizes, there's always an upgrade path within the generation: ie instead of waiting for the new generation to upgrade from 1T to 1.5T, you can upgrade to the next step of 2T in the current generation. This is much lower cost for the vendor (no retooling, just the extra platters/heads).

Theo

But what manufacturing issue determines 1.0T vs 1.1T? Magnetic domains don't have physical boundaries that have to be reshaped.

I.e., why "settle" on 1T (per platter/device/etc) and not 1.2T? Platter dimensions aren't being tweeked so why the "coincidence" in the capacities available?

You need a certain amount of 'raw' data for servo information and for blocks reallocated due to errors. Since round numbers are better for marketing (1T not 1.134T) I expect those hidden areas can vary in size so as to make the advertised capacity a round number.

For operators of multi-disc arrays, having a non-round size is a bug not a feature. If the 1.134T drive in an array fails, you need another 1.134T or larger drive to replace it. The competitor's 1.132T drive won't do.

Theo

Yes. The next version has to be twice as good as the previous version and

Also it's perfectly reasonable to charge twice the price for twice the storage capacity. Isn't it?

So, no "value" to having a larger capacity.

Amusingly, I have seen 1T drives and 1000GB drives from the same vendor (with the same capacity); marketeering?

Yes, hence the creation of DSO.

Often, such models are available concurrently so its a question of what the company decided to "push".

IME (admittedly sorely out of date as I haven't paid for kit in decades), the cost of storage media has dropped (price per bit/spindle) considerably. I recall paying $10K for ten 4G (that's a G, not a T) disks, ages ago.

And, the media is considerably more durable -- I've seen drives with ~100K PoH and *no* grown defects!

Remember when drives were mounted on overdesigned "shock mounts" out of fear the slightest jarring would crash the disk?

Certainly. Customers and end users prefer easily digestible whole numbers. Anything that require math to understand, such as decimal arithmetic, turns off the GUM (great unwashed masses). Western Dismal makes it even simpler for buyers using color coding.

Large numbers sell better than small numbers. There's about a 25% increase in drive capacity when changing from CMR (conventional magnetic recording) to SMR (shingled magnetic recording):

Rotating rust drives are in demand at AI data centers (due to a shortage of SSD drives). HDD volume and margins are decreasing. Long lead times are causing buyers to buy almost anything that spins. The increases in HDD capacity are causing a drop in the number of drives shipped:

Is that decimal or binary TB?

"Why does my hard drive report less capacity than indicated on the drive's label?"

"Storage capacity measurement standards"

Occam's Razor. The simplest explanation is the manufacturer ran out of space on the label. 1T occupies less printing area on the label than 1000GB.

There was a time, when HD manufactures provided labels with everything EXCEPT the drive capacity. These drives had the heads, tracks, cylinders, platters, sectors/track, but not total capacity.

Sure but the buyer will see something twice as big. And twice as big is twice as good. Isn't it?

It seems to have reached a turning point and is now increasing again. Probably because you shouldn't need storage at home. It should be in the "cloud". Shouldn't it?

I remember disks which had to be pulled out of a unit which looked like a top loading washing machine.

There are some advantages to having a small number of well defined drive sizes. Recently I wanted to make an image backup of the 2Tbyte SSD (*) in my laptop PC. I have lots of ex data-centre drives, many of which are "2Tbyte". It turned out that the SSD capacity was EXACTLY the same number of bytes as the spinning disks,so the image fitted perfectly.

• I bought the SSD before prices became stupidly expensive. John

Every drive manufacturer makes it clear that a terabyte is 1000 billion bytes.

Current drives often have the capacity "hidden" on the label. Really? Is there something else that is more important to put on the label??

HGST drives tend to be well labeled -- nominal geometry (which, long ago, lost all meaning), LBA, capacity, interface type, rpm, power requirements, firmware, date of manufacture, S/N, etc.

Along with a dozen logos/certification marks that waste a disproportionate amount of space...

The coloration indicates other drive characteristics beyond capacity (Red drives for NAS use, Blue consumer, Black enterprise, green power saving, gold... )

Shingled recording takes a performance hit. (and, likely, a data reliability hit). It is really only useful for "write seldom" applications (like large consumer external disks acting as archival storage).

But, that doesn't address historical trends.

The amusing question is why PC vendors don't opt for larger drives in their offerings. At their buying quantities, I would imagine doubling the size would cost next to nothing.

It could be that SSDs are now replacing rust drives.

RK07? I used to have an "in" at DECs Maynard facility -- free reign of the "scrap" room. I recall seeing a pair of these where the disk (pack) had crashed "spectacularly". It's one thing to rotate a tiny platter at

I had a *fixed* disk drive (RS03, IIRC) that had 512KB (that's a 'K') of capacity effectively WORD ADDRESSABLE -- at about 500KHz. It weighed a bit over 100 pounds and would dim the lights when starting.

One thing I learned, early on, was never to buy things as they were obsoleted too quickly!

I store images in compressed form -- along with a hash to reassure me of their integrity. A smart image creator doesn't bother storing unused portions of the medium (it has to be filesystem-aware to do so).

E.g., I store several iterations of the "build process" when creating a new Windows box -- on a 250G disk even thought he system may have a 1T drive within. (this is a win if I botch the install and want to rollback to "just after the drivers were installed" or "just before installing the drivers" or...)

One can usually install an image onto a larger medium and "enlarge" the filesystem to fit.

Depending on what is where, you can also often SHRINK a filesystem to fit on a smaller medium.

Standardized color coded HDD are a good thing. Every company should have it's own standard.

Yep. SMR (shingled) drives are amazingly horrible resyncing RAID arrays. Some HDD manufacturers were caught selling SMR drives largely by hiding any information as to whether it was shingles or conventional.

However, drive manufacturers seem to have discovered the benefits of not including any information on the drive label: "More used Seagate HDDs disguised as new: Fraudsters make it tough to spot the difference"

I didn't want to post every graph I found showing sales by unit, capacity, market segment, withdrawn for internal use, refurbished, etc. Which historical trend would you like to see addressed where I failed to address my observation that a volatile and demand driven market is a bad time to compete on selling price?

Marketing again. Drive? What's that? Is that the memory where my pictures are stored? Or is that the cloud?

They are, but I expect that data centres want a lot of them.

Yes, something like that.

Available technology.

You develop a technology that allows a certain density of data per inch. Well, the diameter of the plate is given, so the size in bytes of a plate is thus given, not arbitrary.