MTBF for MX68

[Athers]

Hi, I've been trying to work out some maintenance related budgets and wanted to understand the MTBF for the MX68. I searched the forum and found an old post stating it at 174,600 hours, link below. This seems very low and on an estate of 1000 devices works out at about 50 failures per year. Can anyone confirm if this figure is correct?

https://community.meraki.com/t5/Security-SD-WAN/MX-MTBF/m-p/56273/thread-id/14359 

Many thanks.

[alemabrahao]

I believe this would be a question for your Meraki sales rep or support.

[Athers]

Opened a case and had the following response, I have asked for a rough ball park figure.

"Hello Martin, this is internal information, unfortunately, but I can say the value 174600 is atleast half of the actual value. I will check internally and see if I can share the actual value with you but please know the value you listed is not accurate."

[K2_Josh]

I know that at least as of a few months ago there was official Meraki documentation in a single page on expected failure times for different Meraki devices, although this may have just been switches. But, I can't seem to find this so I suspect that it has been silently removed. I'd prefer to be wrong about it being removed.

[Brash]

I'm not sure whether that information is still widely available. Previous community posts indicate that Meraki Support can provide it.

That said, I'm not sure your calculation is correct.

174,600 hours = 20 years.

Therefore each of your 1000 MX68 has an MTBF of 20 Years.

Dividing the 1000 by 20 to get 50 devices a year doesn't make sense in this circumstance.

[Athers]

Hi, the logic is that the 20 year MTBF is an average, statistically, over 20 years all 1000 will have failed. To achieve that failure rate then 50 a year, on average, will fail. Happy to be corrected if the logic isn't right.

[Brash]

Your logic would indicate that "All MX's should fail before 20 years", which isn't the same as Mean Time Before Failure.

Assumedly MTBF would be calculated from a certain number of MX's and tracking when they fail. Some may be as low as 1 year, some may be as high as 40 (for example). That spread would then be averaged to 20 years.
In the real world, this is probably extrapolated data rather than real lab devices sitting for 20+ years but the theory is still the same.

The other thing to note is that devices don't have a linear failure rate. They usually adhere to some sort of non-linear graph that typically follows a high rate of immediate failures (factory defects), then a very low rate of failures for a certain period of time that eventually begins to spike at the MTBF.