It's faster than comparitively it used to be, it's not faster than raw HTTP, but it isn't far off (excluding negotiating the initial connection). If you're talking about people using SPDY rather than just plain HTTPS, then that's a different matter as well.
That being said, I am not advocating against using HTTPS all the time, I think that would be fine.
You need to answer a few more questions for the best help here.
What's your technology stack (ie. Apache, or nginx + php-fpm, for example)? 2GB RAM also seems awfully low for an 8 core Xeon, however that's not to say it should have any problems running a decent sized IPB installation.
How large is your board, how many posts, topics and concurrent users in general?
It heavily depends on the size of your actual posts as well. Larger ones obviously take longer to convert. We have around 5 million and a beefy server and the normal script for us would have been more than 48 hours of solid run time (I stopped running it after about 24 hours straight).
If you have a large board it may be worth checking out my converter for doing this. I should note that it's completely unofficial but has positive reviews from those who have tried it and can leverage parallel processing on your linux server to speed things up.
Yes in your config you should set that to "utf8", although I believe it's supposed to default to that anyway. There should definitely be an error in your log due to the fact that IPB is reporting an error. You should try to load the website, then check cache/sql_error_latest.cgi or whatever it's called.
With the release of IPB 4 coming in the future, one of the things that is going to hit people with large communities hard is the conversion to UTF-8 if you are not already there. This can be a huge task, and with bfarber's converter , this works fine, but can be very slow as PHP can only run so quickly as it's bound by a single CPU thread. On my forum, which is a total DB size of ~10GB, bfarber's single threaded script takes over 48 hours straight to run. I found this amount of downtime for my live forum to be unacceptable, so I created a fork of his script and used PHP's fork functions to multi-thread it. With 8 cores assigned to the script, I was able to convert this database in just 5 hours under testing. When I did my live conversion, I assigned 12 cores and was able to do it in 3 hours.
This script is aimed at people with large databases, where a conversion would normally take a significant amount of time, and people who are power users and understand server maintenance and configuration.
Please ensure you carefully read the included readme.txt file, and the documentation in the PHP file for the settings.
The database I converted was an IPB 3.4.5 database, but since this is based on bfarber's script from 2010, there's no reason this shouldn't work on pretty much any IPB version in the 3.x.x series, but I will only be officially supporting it on 3.4.5.
This converter has the following enhancements over the original:
[*]Use of PDO directly for DB connections, which gives a small improvement over using IPB's library
[*]Use of PDO prepared statements for multiple inserts meaning less data and less CPU time are used by MySQL
[*]Ability to remap characters post-conversion
[*]Easy to read exceptions thrown to STDERR on query failure
[*]Useful ETA information based on the records already processed
Sorry for the slow response, you are correct, Linux is a requirement for this script. It would be possible to make it run single threaded but ultimately you may as well just run bfarber's script, I am about to issue a patched version of this though which uses a superior third party library for UTF-8 encoding.