nfs load balancing & optimize

[xadoa]

hi,

i'm trying to speed my site up.. it doesn't have much users but it seem very slow .. i can't have member over 400 at a time it will hang and exhausted ... i'm not sure if someone can give me an idea to speed this thing up .. i have quite of the topics in the forums .. i didn't add many hacks except who logged in today, but i disable it, cuz it cost a heavy query ..
I've disable those search index, viewthread/att immediately, run repari-optimize from admincp, etc.. but still does'nt help much.

the second thing is, i was trying to do the load balancing so i was trying to use nfs for the forums i put the *php in the nfs partition and attachment as file in 2 differents local machines to low down the image loading process then connecting to 1 sql db on one machine. all this running on one domain (host). it seem to works fine, but somehow the sql doesn't seem to update on on machine if the post is posted on the other machine even though it is the same sql db and same *php it only update the title of the post but when u click on the title it said invalid post and link untill i have to restart the sql server then all appear as normal. and then the sql transaction doesn't seem to comit properly .. sometime the db just currupt and error.. had to do the myssamchk again in order to start forums. anyone have any experience like this that can give me a hand? thanks in advance.

my forum stats:
38 000 members
46 000 posts (which is weak posting activity)
6.5 gigs in storage, mostly attachment which i do as file system (i can't remove those attachment somehow cuz users still interested in them)

thanks,
XD