HDD still has a point, but as SSD prices diminish, we'll continue to see it drop off.<p>One of the main reasons is density. You can put 32 E1.S EDSFF SSDs in a single rack unit fairly commonly nowadays. It wouldn't surprise me if some 1U chassis did 40.<p>There's also reliability. They're not infallible, but it's looking like AFRs for SSDs might be half that of HDDs. That's a <i>big</i> deal.<p>Of course there's also cost. Prosumer SSDs are about $70-75/TB now, and common PCIe 4.0 U.2/U.3 enterprise and datacenter SSDs are in the $90/TB range. PCIe 5.0 enterprise and datacenter SSDs? "Yikes", is what I'll say. Have fun negotiating with your rep on those. ;) Meanwhile, 7200rpm SATA HDDs can be had for $15/TB. These are retail end-user prices. If you're doing huge volumes as a cloud provider or a huge SAAS business, pricing goes quite a bit lower.<p>-- -----<p>Where do HDDs still make sense? Sustained transfer operations, nearline storage, and as part of a storage tier where you can intelligently hide the HDDs behind SSDs <i>(lots of solutions for this)</i> and get SSD performance most of the time, and guarantee it where it matters. There's many use cases where they just dominate because of their low cost, and the ability to get the performance required for a lot cheaper.<p>Though compared to high-end enterprise SSDs, 7200rpm SATA HDDs are actually still fine for power, typically pulling 6-7W per HDD instead of 11-15W for fairly common enterprise SSDs. Some enterprise SSDs <i>(mostly PCIe 5, mostly E3-based form factors)</i> can pull 25W, if not 40W. Remember, enterprise SSDs don't do things like SLC cache much -- they just have a MOUNTAIN of NAND <i>(plus PLP capacitors)</i> you can read/write from in massive parallelization. There's no ingest drop-off as a result, but you do have to power all that NAND.