I have a BD-RE which has 2x writing speed which is quite slow.
Do the discs have a fixed writing speed or does that depend on the drive? For example, in the future when BD technology goes up and the BD-RE writing speed in drives goes up, and when I use my current disc in a future drive, will that improve the writing speed?
The blu-ray disc itself stores data telling the authoring software the maximum speed it can be written too, however low quality discs often say they support high speeds which will never actually be reached during the burning process.
So the disc sets the speed limit, but it will sometimes set the limit to speeds which can't be reached.
BD 1x ~= DVD 3.5x ~= CD 60x
So your BD writer can write at over double the speed of the best CD writers and at an OK DVD speed. It does seem fairly slow when compared to DVDs but it may not be as slow as you think.
The speed is set by both the drive and the disc, they each have their limits which should be fairly easy to find out.
It's not worth talking about the MB/s speeds, because once you buy a burner and decide on the brand and speed of your blank media, only then will you find the true time in minutes of how long it will take to burn a disc.
You would think that burning only 100MB to a disc would take a very small amount of time, well it does but then it has to write out the rest of the disc which adds a few more minutes. You'll see this as 'writting lead-out' or similar.