HDDs in Laptops over SSDs

Question

I have always wondered why I am taught that moving a mechanical hard drive while it is reading or writing can be detrimental to and can effectively destroy the drive. However, imagining that all laptops had SSDs or possibly Hybrid drives which I don't quite understand yet, why do laptops have HDDs inside them? Are they the same types that are inside desktops but only at a 2.5" form factor? Thanks in advance.

Edit: So 2.5" form factor drives are usually optimised to be more resistant to general bumps and hits a normal laptop would go through in its lifetime?

Answer 1

Hard drives spin constantly and very fast. The technology was developed before latops were ever invented.

PC hard drives have existed in many form factors over the years. Your very first hard drive ever (the IBM RAMAC) was the size of a washing machine. The oldest ones for PC (like the ST-506, ST-412, ST-225) were about the size of a CD-ROM, possibly some models being taller than a CD-ROM. Eventually 3.5" hard drives became standard for desktop PCs (though you did have some odd form factors such as an old type of Quantum hard drive that was as tall as a standard 3.5" hard drive, but the width and length of a CD-ROM drive. Had to put it in a 5" bay.)

I'm not sure 3.5" desktop drives ever made it into laptops - slimmer 2.5" drives are for these. They are compatible with 3.5" hard drives - you can use 2.5" drives in a PC if you want. On old IDE laptop hard drives you needed a passive adapter to convert from the denser array of pins on a 2.5" HDD to that of a 3.5" HDD, but with SATA the connectors are exactly the same. Interestingly, because of the need to have many drives in as small of space as possible, many servers take 2.5" drives as well (server drives are a little thicker than laptop drives). Server drives may also have a SAS interface which will not fit in SATA motherboard sockets (before SATA your server drives were SCSI which was not IDE compatible).

Laptop drives also tend to run at 5400 RPM rather than the 7200 or higher RPM for desktop drives (server HDDs can run at 10K or 15K RPM).

The head of a mechanical hard drive floats above the platter at a microscopic thickness that is smaller than a human hair. There is no way movement and bumps will not affect reading or writing in progress - not sure of specifics like % chance of the head hitting the platter (head crash) or simply being disturbed by movement. But common sense says that bumps, etc. are likely not good for something holding valuable data and spinning thousands of times per minute with a head that is a microscopic distance above the platter. Laptop hard drives spin slower not only to conserve power but I think also to limit bad effects of external movement.

SSDs are the hot new thing. They are coming down in price but mechanical HDDs have gotten dirt cheap. So, if all you care about is price per GB, an HDD still offers a way better deal than SSDs. 6 and 8 TB hard drives are $300+, but a 6TB SSD would likely run $10,000 or higher.

OEMs for consumer computers tend to go with the cheapest option they can. So this is why you still see new systems with a single 1TB mechanical HDD (which is probably $50 now) when 256GB SSDs are really not terribly expensive (about $100).