Why are there 1TB micro SD cards that are the size fingernail and most 1TB hard drives are bigger than my hand?
In: Technology
You must have tiny hands – Modern Solid State drives use the M.2 standard, and are 2cm across, 6cm long and about .4cm thick. And they are that size because that is what the standard is. Companies that want even more compact devices use standards that are smaller still.
SATA SSDs are their size, again, because that is the standard. If yuo were to break open a SATA SSD, you’d find that the circuitry doesn’t take up much of that case.
It is only old school mechanical drives that are about the size of your hand. And these are that size because they spinning platters are abut 7cm across.
A MicroSD card has very limited throughput (read and write speed) compared to a proper disk drive. A really good SD Card can write about 30 MBytes per second. A hard drive can achieve 100MBytes to 200MBytes per second. And a solid state drive can do 500MBytes per second.
So SD Cards are small and cheap, but slow and not robust. Hard disks are cheap, moderately speedy, and robust. SSDs are robust, relatively expensive and very fast.
They are different storage types. MicroSD and other flash storage are loaded on chips whereas inside a hard disk drive there are physical metal platters/”disks” which hold the information. These have also been designed to work across different desktop storage brands with universal mounting capabilities. They are also generally more resilient of a storage medium than flash memory, particularly when it comes to deleted/formatted data recovery. Portable storage has its merits but they are unpredictable at end of life.
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In SD card technology software on the phone or device acts as the hard disk controller allowing the physical chip to be smaller.
In an SSD hard drives a motherboard which also contains the NAND chips acts as the controller. The SSD NAND hard drive is also a slightly more advanced NAND storage medium (think extra features) requiring a larger die size.
Side question, but how much does it cost to produce a MicroSD card? SanDisk’s been dropping the price on their 1TB pretty violently, and it’s got me wondering just how much profit they’ve been able to make per unit.
With solid state hard drives, part of the issue is backwards compatibility. It has to match the size of a magnetic drive to fit security in the case, as well as it has to be large enough for the Sata connector.
Other than the underlying technical reasons, there’s also a matter of standardisation. Hard drives have to be big enough to fit in a drive bay and have the appropriate connectors.
On a computer chip, the only thing that matters is the surface layer. The silicon below the surface is just there for support, so the chip doesn’t break apart during or after manufacturing. So what they can do is to grind away the bottom of the chip until there’s just a paper thin surface layer left and glue multiple of these flattened chips into a single stack, which is still thin enough to fit into a micro SD card.
The disadvantage of this is that this doesn’t work with power hungry parts, since concentrating a lot of heat into a tiny area can easily set the thing on fire. But flash memory uses very little power, allowing it to be crammed into tiny spaces like that.
This should not be confused with MLC flash. That means multi level cell, which is a technology that allows to store more than just one bit within each individual cell.
Different technologies.
The former uses [flash memory](https://en.wikipedia.org/wiki/Flash_memory) which is implemented with transistors which are really small. The latter uses [physical disks](https://en.wikipedia.org/wiki/Magnetic_storage) which also need some sort of motor to spin them and a reader/writer arm.
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