How Reliable Are SSDs?

I was really hoping this would actually contain some failure rates. Compared to this blog post, the wikipedia page for SSDs (https://en.wikipedia.org/wiki/Solid-state_drive) is more informative overall, and also doesn't advertise any cloud backup products.

I used SSDS in a large datacenter database deployment some five years ago. Intel drives with sanforce controllers. Of the thousands of drives I installed I had a handful of DOA another handful of failures when writing maxlba to overprovision by 20% and to export wear smart value. And after a year or two exactly one drive that needed to be pulled a because max re-write reported it was at 70% or write lifespan. Compared to the 10k rpm sas drives that had an annual failure rate of 1 in 20 I counted it a win. Especially because I was getting 4x the performance out of 4 drives as I used to get from 12.

Then again there was a huge difference in failure between people who do SSD well (intel and sandisk) and manufacturers who did things... less well. I remember the OCZ controller would crash and block write operations for a half second while it rebooted. Kinda messed with the write throughout numbers.

@backblaze: Have you done the math to determine the intersection between SSD capacity and cost, and TCO power and cooling costs (versus spinning disk) over the life of drives? Also, would write count be a critical measure for your use case? I would assume not, as backed up bits are mostly static (files split into blocks, blocks saved indefinitely) except when you're performing garbage cleanup of user data when they leave or they've removed the file locally.

There's something majestic about a datacenter with no moving parts except fans.

This is a weird article, it seems targeted at home users, only Stddev is the primary concern the avg home user should have wrt 'reliability' once you get past looking at rather or not lifetime is even long enough, and they don't even address that. It's not "how long does the avg ssd last" its "How likely is my ssd likely to die before its time".

Step 1: Assume every home user doesn't use backup. Most users have at least one important thing on their hard drive that is not getting backed up right now, either because they don't have a backup solution, or because the thing is located in some non-standard location that is not getting backed up. I can think of one thing on my own computer that qualifies for the latter case right now.

Step 2: Now write the article taking step 1 into account. Assume somebody reading this article is going to use it to decide where to store their unbacked up important data.

Nobody cares how long the average case is when its longer than they plan to use the drive.

They care about the likelihood their unbacked up data will be lost because their ssd died before its time.

They care about how well the firmware is designed to handle error cases, does it shut down and refuse to power up or does it go read only? Does minor localized errors in some data cause it to lock out access to all data?

Those are the interesting questions wrt to ssds.

> If you replace your computer every three years, as most users do

If everybody shares that opinion, no wonder software is getting more and more bloated, slow, and unresponsive. My main work laptop is an i3 from 2010. I just replace the hard drives and battery every couple of years. Why on earth should I change the whole machine each 3 years? If everyone did that, that would be terribly wasteful.

It seems BB listens here!

https://news.ycombinator.com/item?id=19174145

Can any SSD controller design engineers comment here...?

What is the primary cause of SSD failures?

Is it flash wear out of all cells, leaving no good cells to write new data as people talk about?

Is it flash wear out only of some critical cells?

Is it that cells degrade over time while the drive is off, and when next powered up, they are too far gone to recover the data?

Is it unrecoverable corruption of critical internal data structures?

Is it unrecoverable corruption of user data (IE. The user could reformat the drive and have it back to a usable state)

Is it hardware failure outside the typical 'flash wear out' model?

Is it firmware bugs (eg. A badly timed power off leaves data in such a state that the firmware can't initialize next time)

Need another run of Tech Report's "SSD Endurance Experiment" with current drives.

Throw some nvme and optane in there, see if we can wear one of those out.

I personally would have preferred to see some actually MTBF or MTTF data. (https://blog.fosketts.net/2011/07/06/defining-failure-mttr-m...)

Yet another article with a focus on gradual wearing rather than suddenly turning into a brick, which is the actual common real-world case.

I would ask if there is a recursive quality emerging: we put ram in front of the rust as cache to make them faster and possibly improve reliability by less random acts and more full block streaming.

So now we do SSD in front of entire disk systems, do we get the same benefit? Does a rust RAID run more reliabily if an SSD acts as frontline storage in some write through model?

That was a frustrating read. You kept scrolling waiting for a table of failure rates like their other posts. But it never came.

I did some work with eBPF measuring block i/o latencies on SSDs a few weeks ago. I wish I had a testbench the scale that Backblaze does to really get some data at scale.

https://www.circonus.com/2019/01/which-block-i-o-scheduler-i...

that kind of failed to answer its own question, i was expecting some sort of data on manufacturer/model/how long in service before failure etc similar to things ive seen for platter drives