User Guide - How to Determine Resource Allocations and Usage
- 24/08/2007 3:33 PM
Applicable Plans: All Plans
This User Guide provides information on how resources work in your VPS service. This information that may help you improve the reliability of your service.
*** Description of Resources ***
There are three primary parameters which control the operation of your VPS service - 1) memory, 2) CPU and 3) data transfer rate (amount of data you can download from your site at a point in time). These parameters are very important because they are the parameters that you are most likely to exceed as your site has more visitors or processes more data. You also have two other parameters to be aware of, 4) disk space allowed and 5) total amount of data transferred. These two parameters do not typically impact the day to day operation of your VPS however, unless you hit the maximum disk space allowed, which can impact your site when that limit is reached. The remainder of this email explains all 5 of these parameters in detail.
*** How are Resources Allocated? ***
The allocation of each resource is proportional to the price of the plan. For example, the $90 plan has approximately three times the allocation of each resource than the $30 plan. This is a rule of thumb that although not exact, is very close to being true for all 5 resources.
*** What Happens When you Hit Resource Limits ***
Your site can crash or have processing issues if you ever need to exceed the allowance of any of these five resources with the exception of the total amount of data transferred. Each resource is discussed below.
1) Memory - It is imperative that you have enough memory to handle your peak usage. Increased processing load, additional site visitors, and other application specific processing can cause memory usage to peak. Your site may crash if you hit your memory limit. The memory allocations are listed in the hosting plans details at http://www.eapps.com/plans.
2) CPU - Generally, the CPU limit does not cause a site to crash, although some applications do have problems when they do not receive enough CPU cycles. Applications will sometimes slow down if the CPU limit is reached or even time out, when the CPU manager rations the # of CPU cycles allocated to your VPS. Customers sometimes assume that the VPS itself, or the server it is running on, are slow when in fact their specific VPS is trying to obtain more CPU cycles than what it is allowed to have.
3) Rate Limit - The data transfer rate limit for the eApps VPS is set quite high, and therefore it is not common that customers encounter problems caused by trying to exceed the limit for their plan. If you do hit the limit your VPS will behave similar to what happens when you hit CPU limits.
4) Disk Space - The maximum disk space allowed is a hard limit. If you reach this physical limit it could cause operational problems for your site. Each VPS has a soft limit (free included) and a hard limit (maximum allowed). You can exceed the soft limit, up to the maximum allowance but there is a fee for usage over and above the soft limit.
5) Total data transferred - There is an allowance of data transfer for each VPS plan. This allowance can be found in the plans listings at http://www.eapps.com/plans. There is no cap on data transfer. If you use more than your allowance in any given day, your site will not be impacted, unless the rate of usage tries to exceed the Rate Limit at a point in time explained previously.
*** How do I Deal with Resource Problems? ***
1) MEMORY
A graph of your memory usage is available on the left hand side on the System tab in your Control panel. This graph shows your actual memory usage. This is a hard limit, you may not exceed 100%, otherwise your site may crash or become unreliable.
You can also see your memory allocation and current usage using the Linux "Free" command from the command line. This command will tell you what your allocation is and what your usage is at that point in time. If your usage is at or near your limit you should reduce your memory usage if possible. Some of the things you can do are as follows:
> Optimize your code - review your processes to identify high memory situations
> Uninstall unneeded applications - some applications are active and consume memory, uninstall them if not needed. Make sure you uninstall them from the System tab of the Control Panel. If they are base applications (i.e. sendmail, apache), you should disable them from the Control Panel.
> Uninstall Spam Assassin - this application consumes a lot of memory. We highly recommend that you use our third party spam service from Postini, which is available to all customers and is highly effective as a complete solution. You may want to consider using the built in control panel spam filters or the Greylist filter application. Contact us for more information on these options.
> Tomcat 4/5 users - upgrade to the latest version of Tomcat 4 or Tomcat 5. The latest version of Tomcat 4 and 5 in your Control Panel have a newer Java servlet wrapper which handles memory heap problems more gracefully. IMPORTANT!!!!!!!
> Tomcat 4/5 users - upgrade to Tomcat 6. Tomcat 6 along with Java 6 are available in our CentOS plans. Tomcat 6 consumes less memory than Tomcat 4 and 5.
> JBoss 3/4 users, - upgrade to JBoss 4.2.1 or higher. This version of JBoss uses Tomcat 6, which has a smaller memory footprint.
> Tomcat AND JBoss users - Make sure that the Heap memory allocated to Java is optimal for your plan, as explained in the Tomcat User Guide at http://support.eapps.com/hsp/tomcat and JBoss User Guide at http://support.eapps.com/hsp/jboss4. Sometimes your VPS itself has enough memory but the Java heap allocation is not optimized.
> Upgrade your plan - upgrading your plan is the easiest and fastest way to address memory issues. Upon the processing of your upgrade order your memory is instantly expanded with no impact on the operation of your site. If you are not sure and want to try the upgrade, we will credit the difference in the cost of the plan you are on and a higher plan for one month. Just contact eApps and ask for a Free Plan Upgrade.
2) CPU
A graph of your CPU usage is available on the left hand side on the System tab in your Control panel. This graph shows your actual CPU usage. Any usage over 100% indicates that you have a high CPU usage. The chart is actually expressing the "load" of your VPS expressed as a percentage. A common target for Linux systems is to keep the load at or below 1. A load of 1 is expressed as 100% in your Control Panel. A load of two would be shown at 200%. Any time your CPU is showing above 100% is an indication that you do not have enough CPU power for your needs.
You may also use the Linux "top" command to see how much CPU you are consuming and also what processes are running. This command shows load as well as the percentage of your total CPU allocation. If your load exceeds 1 or your CPU usage percentage is at or near 100% then you do not have enough CPU for your needs.
If you are at or near your limit during peak processing times, you should consider the following.
> Uninstall active applications - If there are any unneeded applications that are running active processes, uninstall them. Make sure you uninstall them from the System tab of the Control Panel. If they are base applications (i.e. sendmail, apache), you should disable them from the Control Panel.
> Optimize your code - you should explore ways to change your processing profile to minimize concurrent processing requests
> Uninstall Spam Assassin - this application consumes a lot of processing when mail is being processed. You may want to consider using the built in control panel spam filters or the Greylist filter application. You may also want to use a third party spam service such as Postini. Contact us for more information on these options.
> Upgrade your plan - If you have determined that your application is constrained by the CPU allocation, you should upgrade your plan. If you are not sure and want to try the upgrade, we will credit the difference in the cost of the plan you are on and a higher plan for one month. Just contact eApps and ask for a Free Plan Upgrade.
3) RATE LIMIT
As explained before, Rate Limit is an allowance of how much data you can download from your VPS at any time. There is no limit on uploads to your VPS. Unfortunately there is no way to see if you are hitting your rate limit from the control panel or the command line. If your CPU looks fine, and you suspect you may be hitting your rate limit, please contact the eApps Support Department. We will be pleased to provide information about the rate limit and help you determine if you are hitting it.
4) HARD DISK SPACE
You can see your disk usage in detail from the Control Panel. Click on the System tab and view the summary on the left hand side. If you are less than your free included allowance, the graph will show you the percentage usage of your free allowance. If you exceed the free allowance the chart will convert to showing the entire hard limit and your usage as a percentage of the total, with your overage shown in red. From there you can click on the Resources Usage link and see the details of your usage by day and month. If you are at or near your allocation, then consider the following:
> Delete unused files - Please make sure that you do not delete or remove system files. You should only delete files that are in your user directories.
> Delete mail messages - If your users keep mail on the server they should clear out old messages that are no longer needed.
> Delete error logs - Error logs frequently consume a lot of disk space. In addition to cleaning out your log files you should ensure that the source of error file generation is resolved.
> Uninstall unneeded applications - all applications consume some disk space, but the amount is a lot less than if they were installed from the command line. Nevertheless, uninstall them if not needed. Make sure you uninstall them from the System tab of the Control Panel. If they are base applications (i.e. sendmail, apache), you should not uninstall them because they will just be re-installed by the system at some time. The Development Tools by far consumes the most disk space.
> Upgrade Your Plan - As mentioned previously, the physical limit for your plan is twice the "free" included amount. If you exceed the free included amount, there is an overage fee. You can pay the fee or upgrade your plan. Please remember, you can not exceed your physical limit of hard disk space for your plan.
5) TOTAL DATA TRANSFERRED
The Data Transfer allowance will never impact the operation of your VPS because there is no hard limit. If you exceed your soft limit you are billed for your overage at the current rate.
*** How do I Increase My Resource Allocations? ***
To increase your resource allocations you must upgrade your plan. The Upgrade Center tab of your Control Panel provides an easy way to upgrade your plan. As mentioned previously, resource allocations are proportional to the price of the plan.
If you have any questions about the resources for your plan, please contact us at support@eapps.com.
Sincerely,
eApps Hosting