I am trying to choose an SD card to get the best I/O performance for an application which basically does this:
- Writes a 4K 30FPS video stream
- Writes a VGA video stream
- Writes multiple log files of various types (text, ROS bags, etc.)
All of these are done continuously and simultaneously during operation. Naively, for best performance, one might get an SD card with good sequential write benchmarks. However, I had these doubts:
- Does it count as sequential write if there are multiple files being written?
- What about if one task uses much more throughput than the others (4K video vs. log files)?
- Does it count as sequential write if the file is constantly growing/being generated while being written (as opposed to e.g. bulk transferring an existing file)?
So I ask myself: should I look for SD cards with good sequential or random write performance? How can I measure my actual sequential vs. random I/O usage to make a more empirically informed decision?
The platform is an Nvidia TX1 running Ubuntu 18. The TX1 is limited to UHS-I interface, U1 speed class (10 MB/s). The impetus for this investigation is that I/O bottlenecks are lowering the actual FPS of the 4K video being written (frames are being discarded because I/O is not ready).
