CRIO Hard Drive Fragmentation

Question

I'm working on a data logging application for cRIO and I started wondering about hard drive fragmentation. This is something that we've had to worry about in the past on Windows PCs. Our Windows file logging routines preallocate files on disk for the express purpose of avoiding fragmentation when writing to them. Does one ever have to worry about defragmenting a cRIO drive?

Answer 1

As Rolf said, there's no need to defragment a USB flash drive, and in fact doing so could shorten the life of the drive.
On a standard hard drive, the data is arrange in concentric rings. There is a head flying over the disc platter that reads data. Defragmenting puts the entire file into neighboring locations on the disc. This speeds up access to the file because minimal motion of the read head is required to access the entire file, saving the time required to seek to a new location.
Conversely, a flash drive is RAM - Random Access Memory. It is equally efficient to access any location in memory, thus the random access. There's no need to read in sequence, so no need to defragment. It's just as fast to read a file spread across the disk as it is to read one that's in consecutive locations.
Also importantly, each sector of a flash drive has a limited number of write cycles (from about 100,000 to 1 million for newer drives). Most flash drive controllers, including the one in the cRIO, include a wear leveling algorithm that spreads files across the disk to avoid wearing out some sectors faster than others. The controller deliberately fragments files, so defragmenting could increase the rate at which some sectors fail.
I don't see any reason not to use the internal storage of the cRIO, although as with anything else it's a good idea to have a backup if the data is critical. You need to take some care in how you write to the file - it's better to write large amounts at long intervals than small amounts rapidly to avoid excessive writes to the disk. The internal flash is designed to be as reliable as the rest of the unit, and unlike an external USB device it can't get accidentally bumped and damaged or disconnected.