Inquiry about HSU on a MyBB Forum

[wc3garage82]

My account is recently suspended because of HSU (high resource usage) even though the forum's usage is just a few (usually maximum of 5 members online, 1 - 4 guests including search engine robots) and this HSU usually happens around 10pm-4am GMT + 8 i don't know why. it already happens to me twice and on the 2nd time, i try turning off mybb and still same problem occurs. According to the MyBB debug located on the bottom page, a few hours before those time, Server Load was around 8.0 - 12.0 and page generation is usually 1.xxxx to 3.xxxx seconds even though no one is visiting my forum. Is there a server problem / forum problem with those things??

oh btw, in a normal time, mybb debugs what it should load, 0.xx - 5.xx server load and 0.xxx generation time (before 6pm/7pm GMT +

can anyone please help me? its annoying me sometimes.

[wc3garage82]

**bump**
it seems that this thing is on the mysql server ( seems that according to mybb's debug, it takes time to usually getting from sessions/templates table and takes the most time query(in the specified time above) .. is there anything i can do about it. and yes, i'm also using an ajax chat

(Stoli Server)
edit
and also the time when i post this, my site is now querying the database slowly :D (mybb debug )