View Full Version : CPU Usage Question

03-11-2008, 11:59 AM
Hi, I noticed that when creating a service package, it asked me how much CPU to use with a default of 25. Can anyone explain in laymen's terms exactly what that would effect specifically, and also how much CPU does a Reseller 1 or Reseller 2 account have to distribute?

03-11-2008, 03:17 PM
Well I am not sure that I can explain in laymen's terms really unless it is to say "Just leave the default of 25". :)

Here is the info that you can find in the Server Manager manual:

An important aspect of Service Package creation is the implementation of Quality of Service, or QoS. QoS ensures that your hosting accounts receive guaranteed shares of CPU resources.

All hosting accounts are assigned CPU shares. These shares determine how much of the CPU an account will be able to utilize at times when multiple accounts are making requests to a fully utilized CPU.

For example, for two accounts, one with 15 shares and the other with 25, both utilizing the server CPU, the CPU is divided between the two accounts at a 15:25 ratio.

QoS limits are specified at the last step of Service Package creation. For standard resellers, 25 CPU shares are allocated for each VPS available on a reseller plan, plus a 10% buffer. This means that a Reseller with 15 VPS accounts is given 413 CPU shares to divide among all VPS accounts. While you are able to give certain accounts more or less than 25 shares, you are limited to the shares available for your reseller plan. You are strongly encouraged to maintain the 25 CPU shares per each VPS account default.

Dedicated servers are given a pool of 100 CPU shares to divide among all VPS accounts on that server. Note that when dealing with individual servers, the number of CPU shares is irrelevant. The CPU is divided based on ratios.

So the Reseller 1 plan has 7 VPS accounts. 7*25=175 so that means you have a total of 175 CPU shares available plus a 10% buffer (175*.10=17.5) wich gives you a grand total of 192.5 CPU shares. WH seems to round up on this figure so you would have 193 actually. ;)

So what does that mean and how can it be useful to us? I really am not sure. The documentation warns against changing the default but does not explain why we should not. Part of me wishes that they would have simply left this setting out if it was not explained better.

03-11-2008, 03:26 PM
I appreciate you getting back to me. My reasons for asking this question, was simply more to know what my options were. For example, if I had a 15 VPS reseller 2 plan, and decided, I'm only going to use 13 VPS accounts, but I'm going to give VPS account 13 - 75CPU, would it make that specific site load any faster, or serve up scripts any faster etc etc.

Does that make sense? Like if I used it for one of my sites that has a contact management database and I'm wanting that site to respond faster or whatever.

03-11-2008, 03:44 PM
Well I asked the same thing of WH tech once and never got any response to the question. Perhaps the question got lost in some of the other issues that where being delt with. You might try sending in a support ticket with the question and seeing if you have any better luck. :)

Your logic was the same a mine and I thought perhaps that since I do have one site that was very busy, that perhaps I could assign it a package with more CPU and it would run better.

03-11-2008, 03:57 PM
Hey, what can I say? Great minds think alike =)

WestHost - DWinans
03-12-2008, 03:49 PM
Dear Fisher/Shawn,

CPU shares only become useful during times when the physical server is busy. It's a way of dividing up CPU resources at that time. Accounts with more shares get a greater percent of CPU resources than ones with lower.

I believe for the most part you understand the concept. However the key is, this feature is only going to help when multiple accounts are requesting resources all at the same time.

If you have a limit of 15 VPS's to create and you only want to create 13 of them and use the extra shares on a different VPS you are more than welcome to do so. Is it going to make your site load any faster? Yes, it will help with performance while the server is recieving multiple requests from different clients. It will not help all the time.

Why it is discouraged:
1. If you set your VPS lower than the default it will recieve less resources during busy times than most other VPS's on that server.
2. It adds a level of complexity to setting up a hosting account. If you have a lot of VPS's and mess with this setting to much on your accounts you are probably going to lose track of the CPU shares you have used. One day you are going to go to create an account and get a quota/share error and you are going to chime into Technical Support wondering why you cannot create a new VPS when your limit states that you should be able to. You will choose 1 of 3 things after that. You will either order additional VPS's to gain more shares, create that account with less shares, or sift through all your service packages until you find the one with more shares, find what accounts are on them, change the values, re-apply the package and if you have any questions along the way you'll probably be asking Technical Support as well, or sifting through the documentation trying to find answers.

For the most part, people can ignore the feature. For those who it may be useful to, understand what you are setting up, and take note of what changes you have made. This will save you time and frustration in the future.

03-13-2008, 07:44 AM
Thanks David, that really does help clarify things. As I see it, as WH suggest it is really best in most cases to leave this alone since even if a domain is not as busy it could "slow down" at times not because of it's own traffic but because of traffic by accounts that may not even be under your own reseller package.

Good information to know.

03-14-2008, 07:04 PM
Yeah, it makes sense to me and clears things up as well. So what can I do with a website of mine that has a contact management database on it, but it seems like each screen takes a long time to load. What factors effect this? And is there anything I can do with a reseller 2 account to speed it up? Or does that just mean this site really just needs a dedicated server?

03-15-2008, 07:56 AM
I keep wondering the same thing as you. I know that you can install eAccelerator if the page runs on PHP and that keeping your tables optimized via a program like phpMyAdmin can help but beyond that I am not sure. I think I can tell a difference between weather the account is running php4 or php5 but have never really pursued documenting it. I wonder if the amount of extensions installed with PHP could make a difference. The only real way that could be tested is to use a manual install of PHP that was just the bare bones. Of course then you may lose some of the functionality that you need for a script.