Yep. I will do my best to answer the ones I know, but I am sure others will provide answers to any I miss.
The MySQL 'server' is actually many different MySQL servers, so I guess performance could differ, depending on what particular box your database ends up on.
Personally, since hosting with DreamHost, I have not encountered any MySQL related problems on my sites. However, from time to time I do see reports in the forum of others with MySQL issues, so the situation is not perfect, but I doubt it could be in such a shared environment.
Since the databases do not exist on the same box as your site files, MySQL performance is not as fast as on some other hosts, but I have always found the performance to be more than adequate.
As for connection limits. DreamHost measure connections/queries using something they call "Conueries". There used to be hard limits on the number of Conueries you could consume per month, but this is no longer the case.
No, I believe only the CPU resources you use on your actual server is counted towards your CPU minutes total.
Yes. As far as I know, all plan types have the same 60 CPU minute limit.
I don't think anyone other than DreamHost themselves could answer this question. All I can say is that I have not encountered the limits with my sites as yet (far from it).
I do occasionally see posts in the forum from users who have encountered the CPU limit. These users are invariably running PHP based forum software. I doubt it is the forum software itself that causes the problems, more likely plugins that the users have picked up that are not particulary CPU resource friendly.
I believe the normal procedure once you exceed the CPU limit is a warning. You may even be moved to a special evaluation server while you attempt to lower your CPU usage.
You would have to ask DreamHost that. I should note, that PayPal payments are also not accepted if you intend to use a promo-code when signing up.
If you are concerned about the guarantee, I would suggest using a credit card or debit card when signing up.
I can't say I have had too many problems with support. Critical issues are always answered in a timely fashion. Although, non critical issues can take a while (over 24 hours) before you receive a response. This is one area where I believe DreamHost definitely has room for improvement.
If you actually exceed the limits, you will be charged excess fees of $0.10/MB for disk space and $1/GB for bandwidth.
However, if you notice that you are approaching the limits, you can always upgrade your plan or add another plan to your account. This can be done via the panel and does not result in any down time for your sites.
Man, that sure was a lot of questions I hope I didn't miss too many.
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