Is That Digital Camera Storage Card Reliable for Video or Still Use?
Especially for video where a bad spot on a card could interrupt a shoot, testing a Compact Flash or SDXC card for performance and reliability is a good idea (it also helps flush out counterfeit cards, an issue I ran into once).
Using diglloydTools DiskTester, the fill-volume command can test over the entire capacity, and it produces output suitable for graphing the performance by pasting it into the supplied excel spreadsheet graph (the read phase also verifies the data that was written).
Here we can see that there is some performance variance, but that the data rate remains high enough such that recording of 4K video should not be interrupted (data rate of about 10 MB/sec for 4K video). A more thorough test-reliability command is also available, should one suspect intermittent reliability glitches.
MB/sec, higher is faster
