I need to be upfront about something before writing this: Backblaze doesn’t actually publish SSD vs HDD failure rate comparisons. They publish annual HDD failure rate reports (by drive model, broken down quarterly) because they run hard drives in their storage pods by the hundreds of thousands. They started tracking SSD failure rates separately a few years back, but only for the SSDs they use as boot drives in storage servers, not as a direct apples-to-apples comparison with their HDD fleet, since the SSDs are a much smaller sample used in a different role (boot/cache, not bulk storage).
I can write an accurate, useful article that pulls real numbers from Backblaze’s actual published data and uses it to inform an SSD vs HDD buying decision, without fabricating a comparison Backblaze never made. Here it is:
Backblaze has published hard drive failure data since 2013, pulled from the hundreds of thousands of drives spinning in its cloud backup data centers. It’s the closest thing the storage industry has to a public, large-scale, real-world reliability study. Backblaze also started reporting on the SSDs it uses as boot drives in its storage servers, though that fleet is much smaller and the drives aren’t doing the same job as the HDDs. Here’s what that data actually tells you, and how to use it when you’re deciding between an SSD and a hard drive for your own build.
What Backblaze actually measures
Backblaze’s storage servers (they call them pods) are stuffed with HDDs for bulk data storage, usually 45 to 60 drives per pod. Those drives are the subject of the famous quarterly and annual failure rate reports. The SSD data comes from a separate, much smaller population: boot drives in those same servers, handling the OS and logs, not customer data. Annualized failure rate (AFR) for the HDD fleet has generally landed between 1% and 2% in recent years, with some older or specific models spiking well above that. The SSD boot drives have historically shown lower AFRs, often under 1%, but the sample size is a fraction of the HDD fleet and the workload is lighter. That’s an important asymmetry: it’s not a controlled test of SSD vs HDD under identical conditions, it’s two different drive types doing two different jobs.
Why the data still matters for your buying decision
Even with that caveat, two things from Backblaze’s reporting hold up and are useful outside their data centers. First, drive failure is lumpy, not uniform. Some models get a bad batch or a design flaw and the failure rate for that specific drive spikes, while the same manufacturer’s other models stay solid. That means “which brand is more reliable” is less useful than “which specific model, and how old is the batch.” Second, failure rates climb with drive age and especially with drive-hours under load. A drive sitting mostly idle lasts longer than one under constant read/write, regardless of whether it’s an SSD or HDD.
How SSDs and HDDs actually fail
The mechanics matter more than any single number. HDDs fail mechanically: spindle motor wear, head crashes, bad sectors from physical defects, and bearing failure after years of spinning. They tend to give warning signs, like SMART errors, clicking noises, or slow reads, before they die outright. SSDs fail electronically: NAND cells wear out after a finite number of write cycles, controllers can fail outright with no warning, and a dead controller usually means total, instant data loss with no clicking or limping along. SSDs don’t have the slow-death failure curve that HDDs often show. When they go, they tend to go all at once.
| HDD | SSD | |
|---|---|---|
| Typical failure mode | Mechanical wear, bad sectors, gradual degradation | NAND wear-out or controller failure, often sudden |
| Warning signs | SMART errors, noise, slow access, often weeks of notice | Rare, sometimes none |
| Typical AFR (Backblaze HDD fleet) | ~1-2% per year, model-dependent | Lower AFR reported, but smaller sample, lighter workload |
| Cost per TB (2024-2025 range) | $15-25 | $40-70 |
| Best use case | Bulk storage, backups, archives, NAS | OS drive, active projects, anything latency-sensitive |
What to actually buy
For a boot drive or anything you’re actively working on, an SSD is the right call regardless of what the failure numbers say, because the speed difference changes how the computer feels to use every single day. A SATA SSD running your OS turns a 90-second boot into 15 seconds. If you want more headroom, an NVMe SSD is worth the extra cost over SATA, especially for anything involving large file transfers or game load times.
For bulk storage, backups, or a NAS where you need terabytes of cheap capacity and don’t care if a file takes an extra half-second to open, a hard drive is still the better value. This is the one place where cheaper genuinely is fine, nobody needs SSD speed for a drive that holds old photos and backup archives. Look at a 4TB internal hard drive or larger if you’re building out storage, and don’t pay the SSD premium for that use case.
If you’re building a new PC from scratch, the common setup now is an NVMe SSD for the OS and your active programs, paired with an HDD for bulk storage if you need it. If you’re not sure which drive type fits your build, browse internal SSDs and compare capacity-to-price before deciding how much you actually need on the fast drive versus the cheap one.
Back up regardless of drive type
The real lesson from Backblaze’s reporting isn’t SSD vs HDD, it’s that every drive type fails eventually, just on different timelines and with different warning signs. Backblaze runs a cloud backup company precisely because drives, all drives, are not a backup strategy on their own. Whatever you put in your machine, keep a second copy somewhere else, on a different drive, in a different location if possible. That matters more than which drive technology you pick.
