Separate web- and database server: Network configuration

Hi all,

I have around 300-400 simultaneous visitors on my forum (vbulletin 3.6.4). Until now, I have had the mysql-server on the same dedicated server as the apache-server. The server load have been quite high at times (5-10) but the forum has been functional thanks to mysql- and apache-configuration help from this forum.

Now the problem:

Yesterday I moved the database to its own dedicated server. The new server is more powerful than the old one and has faster disks. The database server is not connected to the internet, only to the web server with a GB ethernet cable.

The web server has two separate network cards, one for internet access eth0 and one for the local network with the database server eth1.

I managed to get everything working, but when I opened the board again, the load on the web server sky-rocketed. Even with around 20 visitors, the server load was over 30 and eventually it crashed.

At the same time, the database server seems to be close to idle.

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I have read that this type of problems can occur when there is only one network card:
https://vborg.vbsupport.ru/showthread.php?t=111191

However, my web server has two NIC cards and this makes me think that my configuration is wrong.

I want to have the network setup as in the mentioned thread, i.e., the database server should only talk to the web server.

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So the question is: Starting from scratch, how can i configure my network like that?

On the local network, the web server is 192.168.0.1 and the database server is 192.168.0.2

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Another question: I tried to check the transfer speed of the cable (by scp:ing a large file from the web server to the database server) and at some point I could only get 3MB/s (but sometimes 30 MB/s) even though the server load was really low. From what I can see on both sides, the link is Up with 1000 Mbps full duplex.

Is this normal? If not, does anyone have an idea of what could go wrong here? What transfer speed do you think is required for this setup to work?

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Been trying to solve this all weekend, so all feedback is appreciated.

Regards,
Tommy

EDIT: Both servers are slackware 10.2

[Marco van Herwaarden]

First start by doing a traceroute to check if your traffic really is going over the internal direct link. If that is ok, then i suspect a faulty configured switch in between.