How Does Flash Media Fail?

bhodge writes "Aside from the obvious 'it stops working' answer, how does flash media — such as USB, SD, and CF — fail? Unlike with traditional hard drive, where anyone who's worked with computers for a while knows what a drive failure looks like, I don't know anyone who has experienced such a failure with flash. I've haven't been able to find more than scant evidence of what such failures look like at the OS level. The one account I have found detailed using a small USB drive for /var/log storage; it failed very quickly, and then utterly (0 byte unformatted device), after five years of service in the role. This runs contrary to other anecdotal claims that you should still be able to read the media after you can no longer write to it. So my question is: what have you seen of the nature of flash media failure, if anything?"

Comments

Fail on write

[fishybell]

The biggest difference I've encountered is when traditional hard drives fail, they fail on reading data back.

Flash media fails when you write the data. In theory this means that you can always recover data as you can never write data to bad sectors. In practice the entire media device (CF, SD, etc.) fails at once.

Re:Was there a point to this article?

[Sooner Boomer]

If a cell fails, you can't read or write that cell.

If a gate fails in a page, you lose access to the page.

If a gate fails in the overall control logic, you lose access to the whole device.

Is there something I'm missing? Did you think there were oil changes or brake shoes? It's one silicon chip with metal on it.

What about redundancy and self-healing? How do those work?

Re:In my case

[AKAImBatman]

Washing machines are pretty harsh places. You get tidal forces that will apply various physical stresses to the components. Rapid heating and cooling can cause expansion problems. Water can wear down contacts. Soaps can contaminate contacts or have negative chemical effects. So on and so forth.

If it makes it to the drier, your card could easily end up at temperatures outside the optimal storage temperature for the device. (Ever read those warnings, "Store between 70F and 100F?" Yeah, me neither.) These extreme temperatures combined with the rapidity at which they're introduced is a cornucopia of ways your device could be damaged.

In short, water isn't the real problem. It's all the stuff above and beyond that.

Re:In my case

[ptomblin]

Usually the case falls apart. I can still get the data off the drive, but I stop using it and just spend another $20 to get something with 8 times the capacity of the last time.

Re:In my case

[AKAImBatman]

However since i'm lazy i don't want to hold it in forever so it's been retired.

There's a fix for that. :-P

Re:Was there a point to this article?

[Vellmont]

Is there something I'm missing?

Maybe the part where you assume everyone knows the above?

Or how about the part where the submitter is asking about typical failure modes, not all possible failure modes?

Re:In my case

[Bakkster]

Don't forget about the extreme static charges built up in a drier. Even though most USB devices have mechanisms to prevent static damage, a drier could overwhelm these protections. Regardless, usually a SSD failure should usually be due to the failure of the suport electronics, not the storage itself.

Re:flash faliure

[clone53421]

Actually, the rule of thumb is:

backup your data, ESPECIALLY when it's on a flash based drive