CentOS 5.5 +Virtualmin slowdowns

Help! (Home for newbies)
1

Hello,
To cut the chase :
The server has some slowdowns ( most of the time). I got some 500 error until yesterday when i changed some settings here and there following what i found with the help of google here and on some other forums. I got rid of the 500 error but the slowdowns are still there and i have no clue what to look for any more.

  • i have 56 running processes

  • 1 domain +1 subdomain (virtual server + sub virtual server)

  • 1 small website with 4-5 pages on the main domain

  • 1 forum ( not running - still working on it) on the subdomain)

    System configuration :

  • CentOS 5.6

  • Webmin version 1.540

  • Virtualmin version 3.84

  • Kernel and CPU Linux 2.6.18-238.5.1.el5.028stab085.3 on i686

  • VPS 1GB RAM, 2GHz CPU

Other info that may help :
CPU load averages => 0.40 (1 min) 0.89 (5 mins) 1.09 (15 mins)
Running processes => 56
Apache version => 2.2.3
MySQL version => 5.0.77
BIND version => 9.3.6

My question : Is there a way to get rid of the slowdowns ? (or should i back up the virtual servers and just reload the OS, update the restore the Virtual servers)

Thank you,

PS. I forgot to add that i’m new to Linux and hosting.

2

Howdy,

Can you describe the slowdowns you’re seeing? What’s slow exactly? Is it one or two sites in particular, or everything?

If you run the commands “uptime” and “free -m”, what output do you receive?

-Eric

3

I run the commands and i get the following output :
[root@v-470 ~]# free -m
total used free shared buffers cached
Mem: 2048 363 1684 0 0 0
-/+ buffers/cache: 363 1684
Swap: 0 0 0

[root@v-470 ~]# uptime
23:15:36 up 20:00, 1 user, load average: 0.36, 0.72, 0.57

The slowdowns usually lock me out of the system. Meaning that the SSH session usually gives me time out’s, if i try to use the virtualmin web interface i get the same thing. If i’m lucky after a few attempts i manage to reboot it and the everything is ok for a while. The websites are loading very slow ( that is if they are loading at all). I have Ajax chat in one subdomain ( maximum 4 users online), a forum ( not launched yet so has little or no traffic at all) 1 website on the main domain that has no fancy scripts.
( Now it’s 19.21 GMT and the fun is on again :(.

4

Well, your load average and available memory all look okay.

You may be resource constrained in some way. Based on your “free” output, I have a suspicion that you’re using a VPS of some sort… perhaps OpenVZ?

It’s possible that you aren’t being given enough CPU or disk resources. If your load average isn’t going above a 1.00, the sites on your server really aren’t generating much of a load.

Another avenue to explore is that it’s possible that your available bandwidth is the issue.

Does your provider offer bandwidth (and other resource) graphs? If so, you may want to review them and see if they show that you’re using a lot of resources. And if you aren’t, you may want to speak with them about how slow things are for you.

-Eric

5

Bandwidth is not the issue. I have attached a screenshot from the VE Portal interface and one from the Virtualmin interface with the resources.
I just noticed one thing my Virtualmin interface ( and webmin) was shut down.
[root@v-470 ~]# /etc/init.d/webmin restart
Stopping Webmin server in /usr/libexec/webmin
/etc/webmin/stop: line 4: kill: (1791) - No such process
Starting Webmin server in /usr/libexec/webmin

6

Yeah, it’s certainly sounding like you could be running into resource problems with your VPS or provider. Those are all very atypical issues :slight_smile:

What output do you receive if you run this command:

cat /proc/user_beancounters

7

I got lost on this. Thank you for all the help. Hope it’s not too much trouble.

[root@v-470 ~]# cat /proc/user_beancounters

Version: 2.5
uid resource held maxheld barrier limit failcnt
154: kmemsize 8614151 11161711 1 1055923 11377049 38955
lockedpages 0 8 256 256 0
privvmpages 91981 169025 524288 524288 0
shmpages 5353 5721 21504 21504 0
dummy 0 0 0 0 0
numproc 71 109 240 240 0
physpages 39002 97416 0 2147483647 0
vmguarpages 0 0 262144 262144 0
oomguarpages 39084 97416 262144 262144 0
numtcpsock 24 66 360 360 0
numflock 8 21 188 206 0
numpty 1 1 16 16 0
numsiginfo 0 92 256 256 0
tcpsndbuf 214984 731072 1720320 2703360 0
tcprcvbuf 214112 1728112 1720320 2703360 6
othersockbuf 255288 1127248 1126080 2097152 16
dgramrcvbuf 0 262104 262144 262144 209
numothersock 149 283 360 360 0
dcachesize 862002 979447 3409920 3624960 0
numfile 2673 3406 9312 9312 0
dummy 0 0 0 0 0
dummy 0 0 0 0 0
dummy 0 0 0 0 0
numiptent 26 26 128 128 0

8

That output shows various limits that are imposed on you by the OpenVZ container your provider has setup.

We can then use that output to see if you’re seeing failures due to those limits.

And it does look like you are, although not the ones I expected to see :slight_smile:

There’s a “failcnt” column at the very end that you can use to see if OpenVZ has prevented you from getting a resource that your system requested. Anytime that happens, something bad can occur :slight_smile:

The “kmemsize” has gotten quite a few, which is troubling. That’s a kernel memory related parameter.

You’re also seeing some failures with “dgramrcvbuf”, “othersockbuf”, and “tcprcvbuf”. Those parameters are all related to networking.

What each of those means is all described in more detail here:

http://wiki.openvz.org/UBC_secondary_parameters

The thing to note though is that what you’re seeing doesn’t occur on a normal system :slight_smile: Something abnormal is going on, which is likely related to the limits setup for your system by your provider.

You may need to talk to them about the trouble you’re seeing.

However, also note that these problems don’t tend to come up on, say, Xen-based VPS’s :slight_smile: So if you continue to have problems, you may want to consider a different type of VPS.

-Eric

9

Now i finally got it. Well . The VPS is less 4£ / month but i will talk to them as it’s not what they advertise. I will e-mail them right now.
On the other hand i’ll try to find another cheap unmanaged VPS ASAP as i can’t afford a dedicated one now.

Once again thank you very much for all your help.

10

Forgot to ask. Would loading another OS then restoring my backups solve the problem ?

Small edit. I read some stuff on a few forums about fanatical VPS and i’ll give them a go if the guys here do not solve the problem until tomorrow noon.

11

Howdy,

Well, it sounds like the problems you’re having are issues with resources… so no, loading another OS wouldn’t help that issue, unfortunately.

As far as VPS providers – I can’t speak to that one in particular… the only thing I can offer is that the forums here are littered with people who ran into the strangest of issues on OpenVZ based VPS’s. With the way it handles limits, strange things can come up in varying circumstances.

There are of course folks who’ve had great luck with OpenVZ. The experience folks have may well be in how well the setup is of a particular provider.

But, I’ve heard of very few complaints from people on Xen-based VPS’s :slight_smile:

When choosing a provider – one thing I’ll offer is that, at a minimum, you’d want 512MB of dedicated RAM.

Xen-based VPS’s allow you to have swap, so even when they offer only 512MB of RAM, you can use a lot more than that.

OpenVZ systems don’t have swap, they instead offer “burst” RAM. But burst RAM isn’t dedicated memory, and any process using burst RAM could be killed off at any point to make room for processes on another users VPS if the host runs low on memory. Which can lead to really strange things happening :slight_smile:

If you’re interested in learning a bit more about what goes on under the hood, there’s a nice writeup on how all that works here:

http://maxgarrick.com/understanding-openvz-resource-limits/

12

As fas as i understand they are way better so now i’m looking for a cheap unmanaged XEN one. Thank you for the tip. I’ll post back after i find one in case anyone else is interested.