Need some advice before I go postal

[MrEyes]

Hello all,

I am experiencing a number of problems with my current hosts, and need some advice before I go postal.

For just over a year I have been running my forum on a VPS with the following specification:

VPS Host Server: Dual Quad Core Intel Xeon 2.5 GHz 2x6 MB Cache / 12 GB RAM
VPS OS: Linux CentOS 5.0
VPS Guaranteed RAM: 2gb Guaranteed (no burst)

The host refers to this package as semi dedicated as they guarantee that a single hardware host will only host a maximum of 6 VPS images.

Up until around 2 months ago everything has been running fine and the server has happily handled the requests made of it. However in the last 2 months and at seemingly random time the load sky rockets and the server dies.

Of course when I first raised this with the support desk their response was that the server was overloaded and I needed to upgrade to a fully dedicated package, however this just didn't seem right to me as I knew from Google analytics that the volume of traffic today is not really any different to what it was a year ago when everything ran fine. To demonstrate this here are the analytics page view stats for the last year

• 03/2008 - 1482690
• 04/2008 - 1374737
• 05/2008 - 1276575
• 06/2008 - 1345278
• 07/2008 - 1325454
• 08/2008 - 1168109
• 09/2008 - 1286918
• 10/2008 - 1376495
• 11/2008 - 1413101
• 12/2008 - 1289283
• 01/2009 - 1301078
• 02/2009 - 1201745
• 03/2009 - 1196358

However no matter how I put the fact that usage has not change in the last year the host is sticking to their "you need to upgrade to dedicated" position.

So I then decided to do some more specific monitoring, so for the last week I have been running a cron job that every ten minutes queries OS load stats and vbulletin user stats and outputs these to a file, this has shown something rather interesting - for example:

• 03/04/2009 @ 12:00, 139 users online, Load stats 0.39, 0.55, 0.76
• 06/04/2009 @ 12:50, 138 users online, load stats 0.39, 0.54, 0.92
• 02/04/2009 @ 22:30, 118 users online, load stats 0.37, 0.71, 1.1

All good, everything is running perfectly, however:

• 06/04/2009 @ 09:40, 94 users online, load stats 11.63, 6.63, 3.46
• 07/04/2009 @ 08:51, 6 users online, load stats 26.19, 8.65, 3.17
• 07/04/2009 @ 21:21, 115 users online, load stats 101.64, 58.92, 27.41

Now the host is saying that it is obvious that users are "using the site" in a different way and are therefore causing the outages - again this doesn't make any sense - how can the activity of 6 users cause more load than 139 users? So far the host has skirted around the answer to that question like a well practiced politician.

In addition to this every time there is an outage, I get a slightly different reason for the outage before the classic "you need to upgrade" line is produced, so far I have seen everything from "MySQL is not optimised for VPS" to "MySQL connection limit was reached" even though this is set at 750 and I have never had 750 users online let alone 750 all querying the DB at the same time.

So the question is, who is right? me or the host?

[snakes1100]

Well, without debugging the system, checking logs etc, can't really say, but i would bet its most likely the server over loading and not from the 6 users on your site.

Have you debugged the server?

[motowebmaster]

Sounds like you've done your research, but there could be several reasons why your CPU load is that high, some of which have nothing to do with vbulletin.

Possibles could include:

• purposeful action (such as a DDOS)
• problems with email (high rejection or scanning)
• restrictive config settings in either apache, php, or mysql
• servers that also host DNS
• search engine spiders indexing your content

I think your host's feedback is questionable, but it is entirely possible that all of your application activity is valid and needs to be addressed.

One of the books I keep close, titled "Linux Server Hacks", offers some scenarios and suggested practices for determining the cause of utilization issues.

[TigerC10]

Some hosting companies will offer VPS and then artificially enduce problems to convince you to get a dedicated plan. Is your host a trusted host?

[MrEyes]

Originally Posted by TigerC10

Some hosting companies will offer VPS and then artificially enduce problems to convince you to get a dedicated plan. Is your host a trusted host?

I have nothing to back this up but this is the "feeling" I get, as everytime I speak to support the outages are caused by a different reason. So far we have had the following:

• General volume of views
• More than 500k rows in the vbulletin "post" table
• MySQL not optimised
• Too many connections to the db
• To many HTTP processes
• An single IP making too many connections (this IP is now firewalled out on the hardware firewall)
• Insert random reason here

If the reason was constant I would be more inclined to believe them, but it isnt.

I intend to really start marketing my site in the next few months, so I do intend to go dedicated however the chances are it won't be with this host.

[royo]

If you're paying a really low amount for that VPS it might be oversold and so you will see problems.

[Marco van Herwaarden]

Try posting in the server configuration forum at vB.com, maybe they can give advise on tuning the server a bit more.