I’m kinda curious as to why everything hasn’t just shifted over to these tiny, affordable little guys. They can have so much on them!
In: Technology
As others have explained, SD cards are built to be physically small and power-efficient. So they typically incorporate just one actual flash chip (and the term chip here is loosely used as it’s probably a single combined storage and controller chip all moulded into the body of an SD card directly). Flash chips are limited in performance, so a computer SSD will often incorporate multiple actual flash chips so that accesses can be striped across them, improving performance. Computer SSDs can also incorporate things like DRAM chips that their controllers can use to help improve performance even further. For an SD card in a camera or a phone, all of these things are unnecessary (performance is good enough!) and it would be better to just devote that space to storage.
As for why do we use hard drives still, the short answer is that they still provide more economical storage than SSDs. But that gap has been closing for awhile now. We’re at the point where it only really makes sense to use a hard drive if you have a lot of data to store.
Embedded computers and cheap laptops frequently do use them. eMMC is basically just an SD card soldered onto a motherboard.
It only makes sense when you’re squeezing cost though. For marginally more you can get much faster storage.
eMMCs are exactly this. Usually found in <$300 laptops. Other commenters have explained well why these are budget drives.
SD Cards are generally made with the NAND chips that fail to pass the quality control checks for SSDs. They generally have really slow read and write speeds due to being a single NAND chip and they do not have much in the way of longevity when it comes to writing data due to how NAND degrades with writes and a complete lack of wear leveling.
SSDs on the other hand, despite being based using the same NAND technology, have a controller which handles things like wear leveling and communication with multiple NAND chips at the same time to vastly improve read and write speeds. The addition of DRAM caches helps to improve read and write speeds even further as well as providing scratch space to use for wear leveling techniques. Capacitors add in loss of power protection to help prevent data corruption when power is lost mid-write.
In other words, SSDs are far superior to SD cards when it comes to reading and writing data and will last much longer when doing so. SD cards are useful to storing data that isn’t required to have constant reads and writes and is easily removed to transfer the data. They will never replace each other while we still use NAND technology.
i guess sd cards are cool and all but they’re not as reliable like hard drives or ssds. plus they can get corrupted really easily. bigger storage means better safety you know. capacity is sweet but durability is key too.
SD cards have slow read/write speeds. 40mbps is average for a SD card, compared to a “average” SSD’s 4,000mbps
SD cards cannot withstand as much write cycles before failure. An sd card stuck into any device that constantly writes to it, like a dashcam, will usually fail within a year unless you buy special endurance ones. A SSD can typically take constant writes for many years in comparison.
SD cards are limited to the speeds of USB adapters or SD card slots, a UHS-II SD card maxes out at around 300mbps, so you simply cannot go faster without making a new interface/standard.
Due to their small size, they cannot dissipate heat well, so during intense read/write sessions, they will heat up and degrade faster.
SD cards are often made with cheaper components with lower lifespans.
its all down to buisness, people could make SD cards in droves for higher storage density but then that would ruin the market and kill margins, so no company will do it.
same reason why 8tb SSDs are insanely expensive and why HDDs get very non-linear in price as you go above 10tb. our global economy has frozen all storage costs because everyone wants high margins, nobody cares about high volume.
Its the exact opposite world we had when DVDs and CDs were a thing thats for damn sure.
also all the people saying its for technical reasons are wrong, a 40tb microsd based SSD would still be better than a HDD, even if it might be slower than modern full size flash chips
[This SD Card has a read/write speed of 160/90 mb/s](https://www.amazon.com/SanDisk-Extreme-microSDXC-Memory-Adapter/dp/B07P9W5HJV)
The absolute cheapest SSDs you can find on the market have a read/write of 1000 mb/s, with most gaming SSDs boasting 5000 or even 7000 mb/s
They’re dreadfully slow and really only useful for low end systems like the Switch or Steam Deck
Think of it this way, everything has a purpose.
The point of an SD is to be small, compact, and suitable for mobile devices such as camera’s, phones, or your Switch.
An SSD is meant to be fast. It has a limited lifespan, like the SD card, in terms of how much it can re-write, but it is incredibly fast. That’s why they’re used by hobbyists and gamers for storage.
A HDD is commonly used for things that need a lot of re-writes, or bulk storage. In terms of $ per GB, HDD’s are still the king, though SSD’s are catching up.
And just to throw a neat factoid at you. Magnetic Tape is still used. Though, afaik, it’s really only used for long term storage of system backups.
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