I am currently on an old hostgator VPS server. They will give me about 75% off if I transfer to their new VPS servers for a 3 year period if I buy upfront, which seems like a good deal. However I think my site might need a dedicated server, due to CPU load issues. My server load as reported by Parallels Power Panel resources section is often over 50%. I also see this in the resource alerts:

Sep 10, 2016 07:10:26 PM      Resource      Resource dcachesize green alert on environment web.ozpolitic.com current value: 16118710 soft limit: 26210000 hard limit: 26210000      Green zone      dcachesize
Sep 10, 2016 07:04:26 PM      Resource      Resource counter_cpu_share_used green alert on environment web.ozpolitic.com current value: 73 soft limit: 85 hard limit: 95      Green zone      counter_cpu_share_used
Sep 10, 2016 07:03:26 PM      Resource      Resource counter_cpu_share_used red alert on environment web.ozpolitic.com current value: 95 soft limit: 85 hard limit: 95      Red zone      counter_cpu_share_used
Sep 10, 2016 07:01:27 PM      Resource      Resource dcachesize red alert on environment web.ozpolitic.com current value: 26208624 soft limit: 26210000 hard limit: 26210000      Red zone      dcachesize
Sep 10, 2016 06:59:26 PM      Resource      Resource counter_cpu_share_used green alert on environment web.ozpolitic.com current value: 7 soft limit: 85 hard limit: 95      Green zone      counter_cpu_share_used
Sep 10, 2016 06:58:26 PM      Resource      Resource counter_cpu_share_used yellow alert on environment web.ozpolitic.com current value: 78 soft limit: 85 hard limit: 95      Yellow zone      counter_cpu_share_used
Sep 10, 2016 06:40:26 PM      Resource      Resource dcachesize green alert on environment web.ozpolitic.com current value: 20704565 soft limit: 26210000 hard limit: 26210000      Green zone      dcachesize
Sep 10, 2016 06:34:26 PM      Resource      Resource counter_cpu_share_used green alert on environment web.ozpolitic.com current value: 23 soft limit: 85 hard limit: 95      Green zone      counter_cpu_share_used
Sep 10, 2016 06:33:26 PM      Resource      Resource counter_cpu_share_used red alert on environment web.ozpolitic.com current value: 90 soft limit: 85 hard limit: 95      Red zone      counter_cpu_share_used
Sep 10, 2016 06:20:26 PM      Resource      Resource dcachesize red alert on environment web.ozpolitic.com current value: 26205025 soft limit: 26210000 hard limit: 26210000      Red zone      dcachesize
Sep 10, 2016 06:05:26 PM      Resource      Resource dcachesize green alert on environment web.ozpolitic.com current value: 19143814 soft limit: 26210000 hard limit: 26210000      Green zone      dcachesize
Sep 10, 2016 05:26:25 PM      Resource      Resource dcachesize red alert on environment web.ozpolitic.com current value: 26203728 soft limit: 26210000 hard limit: 26210000      Red zone      dcachesize
Sep 10, 2016 05:16:26 PM      Resource      Resource dcachesize green alert on environment web.ozpolitic.com current value: 15131116 soft limit: 26210000 hard limit: 26210000      Green zone      dcachesize
Sep 10, 2016 04:42:26 PM      Resource      Resource counter_cpu_share_used green alert on environment web.ozpolitic.com current value: 0 soft limit: 85 hard limit: 95      Green zone      counter_cpu_share_used
Sep 10, 2016 04:41:26 PM      Resource      Resource counter_cpu_share_used yellow alert on environment web.ozpolitic.com current value: 84 soft limit: 85 hard limit: 95      Yellow zone      counter_cpu_share_used
Sep 10, 2016 04:38:26 PM      Resource      Resource counter_cpu_share_used green alert on environment web.ozpolitic.com current value: 41 soft limit: 85 hard limit: 95      Green zone      counter_cpu_share_used
Sep 10, 2016 04:37:26 PM      Resource      Resource counter_cpu_share_used red alert on environment web.ozpolitic.com current value: 89 soft limit: 85 hard limit: 95      Red zone      counter_cpu_share_used
Sep 10, 2016 04:33:26 PM      Resource      Resource dcachesize red alert on environment web.ozpolitic.com current value: 26202027 soft limit: 26210000 hard limit: 26210000      Red zone      dcachesize
Sep 10, 2016 04:31:26 PM      Resource      Resource dcachesize green alert on environment web.ozpolitic.com current value: 15497554 soft limit: 26210000 hard limit: 26210000      Green zone      dcachesize
Sep 10, 2016 04:00:27 PM      Resource      Resource counter_cpu_share_used green alert on environment web.ozpolitic.com current value: 0 soft limit: 85 hard limit: 95      Green zone      counter_cpu_share_used
Sep 10, 2016 03:59:26 PM      Resource      Resource counter_cpu_share_used red alert on environment web.ozpolitic.com current value: 89 soft limit: 85 hard limit: 95      Red zone      counter_cpu_share_used

AWstats was already disabled. I also disabled the other two stats packages, which did not make much difference. 

I have not done anything to stop bots crawling the forum. Would that make much difference? Note that I want the search engine bots to crawl my site if that gives the site better google rankings. I have google ads running on the forum that cover the hosting fees and then some, and forum posts often get a high position on google for issues currently in the news, so I am happy to pay what it costs to keep those bots happy.

It looks like most of the resources would increase, such as disk space and bandwidth, but I am a long way off using those. It looks like CPU is the limiting factor, and the host themselves told me it would be pretty much the same under the new package.

Is there a simple way to block unwanted bots, and how much difference is it going to make?

Unfortunately the good deals are only on VPS, not dedicated. The hostgator tech support keeps plumbing new depths of hopeless. They cannot even give me consistent advice on what type of server I need. I will probably jump ship, but am too busy for the next month.

YaBB seems to be the main culprit. Is there some built in metric in YaBB that I can use as a guide for what sort of server it needs? Can you just tell by frequency of new posts?

.pl files make up over 80% of my bandwidth. There was one Russian website with 300 links over the last few days, which is probably hotlinking, but not significant at the moment.

Looks like there are a few bots crawling so I will look into that. The 'unknown' bot had over 100000 hits and 10GB of bandwidth in about 3 days, which is about 20% of the bandwidth.

Hostgator just put their dedicated hosting on special, so I think I'll just bite the bullet and get 3 years of that. Fingers crossed they don't go out of business.