Filesystem performance overheads 4209

sg You will probably have to do this with your own machine under the conditions you are really running under with the programs that really concern you.

Imagine that the file system is 1000x slower in some sense than the RAM, but that you do little IO between the compute-limited processing of whatever it is you are reading or writing. Then the IO performance overhead would really be of no interest, and if speed is a problem, the processing algorithms would need improvement, not the IO.

At the opposite extreme, imagine your process were completely IO limited. Then the file system overhead would matter a lot. But if you run a 5400rpm hard drive with a tiny buffer using IDE interface transferring a byte at a time, this could be serious, whereas if you run a 15,000 rpm Ultra-320 SCSI hard drive with an 8 Megabyte buffer and your OS chains the SCSI commands, the file system overhead can be considerably less. Also, if you run Linux, you can have an enormous amount of stuff cached in RAM even with the file system in use, and avoid doing a lot of IO if you have enough memory for the cache.

Only after you have considered all these issues does the question of the file system used begin to be of interest.

But with all these (and other) variables, you can see why no one would bother doing such a study. It would take too much time to do, and too much space to print the results that would be of very limited interest.

-- .~. Jean-David Beyer Registered Linux User 85642. V PGP-Key: 9A2FC99A Registered Machine 241939. ^^-^^ 07:50:00 up 17 days, 1:28, 4 users, load average: 4.23, 4.21, 4.11