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I was looking around for a cheaper SSD on Newegg and the time I'm writing this they have almost 300 2.5-inch SSD but only 12 3.5-inch ones, 9 of which are sold out. Why are there so few 3.5-inch SSD? Is it just that the demand for these drives is mostly in laptops? Why should I have to pay more for a (physically) smaller drive and then have to pay more again for a mounting piece to stick it in my computer?

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    There's no need for a larger form factor - the storage density is good enough for most people. Also, most manufacturers provide a 2.5-3.5" mounting adapter for free, and nearly every computer case that's manufactured now includes support for 2.5" SSDs. Mar 8, 2012 at 19:09

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I think it comes from a handful of factors:

  • Demand. For the last few years, laptops have been outselling desktops. Want to make a product appeal to the largest possible audience? Make it work with a laptop.
  • Compatibility. Since mounting kit adapters exist and are relatively inexpensive, making the drives 2.5" allows for the most users.
  • Many new desktop and server case designs have at least 1 native 2.5" drive mount. In some cases it's to allow for SSD usage, in others it's simply a matter of density -- you can fit quite a few more 2.5" drives in the same space as 3.5" drives. You see this more in server cases than desktop cases though.
  • Physical Space. Part of the reason that 3.5" hard drives still exist (besides inertia) is that they allow for larger platters, which allow for higher capacity drives. A large enough SSD to require a 3.5" design would be prohibitively expensive.
  • Manufacturing. It costs less to build 1 enclosure design than it does 2.

There's probably a few other things, but those all come to mind off the top of my head.

Finally, since an SSD doesn't have any moving parts, it's not prone to moving around inside a desktop system. Unless your system uses a tool-less mounting system that requires 3.5" SATA drives with the power and data connectors in the appropriate place (e.g. Mac Pro, Dell OptiPlexes, etc.), you can just use a piece of velcro, a plastic wire tie, double-sided tape, or any other solution you can think of to keep the drive from moving very far.

For the few desktop systems I deploy that have SSDs, I just leave the drive sitting at the bottom of the case if there's no other way to mount them properly. It's far cheaper than buying additional kit just to mount them "nicely". Those systems have plenty of thermal headroom such that heat simply isn't an issue.

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    Plus brackets are $2.
    – surfasb
    Mar 8, 2012 at 21:08
  • Very well answered and comprehensively explained.
    – Prasad
    Feb 1, 2013 at 18:34
  • Do you have a pic of many 2.5" drives in a 3.5" bay?
    – barlop
    Oct 9, 2015 at 12:01
  • @barlop: That is slightly confusingly worded. What I was referring to are storage servers with multiple drive bays. e.g. In a 2U rackmount enclosure, it's possible to fit more 2.5" drives than 3.5" drives. That said, products like the Icy Dock MB082SP allow for installing two 9.5mm 2.5" drives into a single 3.5" half-height bay. That was simply the first product I found on Google, not an endorsement for that particular item.
    – afrazier
    Oct 9, 2015 at 15:05
  • I can really transition my 7-bay NAS to 3.5" SSDs. Can you fit 4TB of current SSD tech cheaply enough into a 3.5" housing? Given general move to phones/tablets/ultra-thin laptops and distrust/cost of clouds SOHO NASes are too soon to write-off. I would love more reliable, faster, and bigger storage plugged into my existing infrastructure. Adapters seem to be a half measure. Sep 7, 2016 at 21:40

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