In-Depth Followup to the cPanel/WHM Admin Essentials 30-Minute Webinar

[cPanelDavidG]

We understand you may have questions that cannot be swiftly answered in just a minute during the Question and Answer session of the cPanel/WHM Admin Essentials 30-Minute Webinar. This forum thread is a venue where you can ask longer, more in-depth questions.

[daniel_onnet]

how do one make use of "sar" or "iostat" command, or sysstat utility in general, for debugging server load on a cPanel server.

If it's allright with you, I'll break this out into it's own thread and respond to this in a day or so; it's a pretty in-depth question (and a good one). Thanks!

[free-admin]

What is the best OS for WHM (Linux or freebsd)?

The best OS for you to use is the one you are most comfortable with. If you're very familiar with FreeBSD, then by all means use that. If you're more familiar with Linux, then it's probably your best choice. With that said, Linux (CentOS/RedHat) seems to be the most popular platform with cPanel/WHM, so that may factor into your decision (the more people that run software with a particular configuration, the larger your peer support pool).

[Datcrack]

How can we limit PHP Memory usage. Some scripts create a loop and eat up servers memory which causes swap and eventually high server load.

[BWS]

I've had some in-depth discussions this week about using cloudlinux (cloudlinux.com) to limit resources on a per account basis (almost like a VPS but at a cPanel account level). Is this recommended or do you have any views on it?

Specifically this would be to stop one users processes overloading the system?

[Alejandro P]

Regarding a high WA, would spread accounts on additional disk reduce the server load?

[agudiel]

Is there a way to create a limited CPanel user, with access only to email and ftp accounts but not to databases and content?

[agudiel]

How can we limit PHP Memory usage. Some scripts create a loop and eat up servers memory which causes swap and eventually high server load.

I would suggest checking this on WHM:
Main >> Service Configuration >> PHP Configuration Editor
- max_execution_time and memory_limit

[Metro2]

In the webinar you mentioned I/O waits are one of the bigger issues in performance, and that's in the neighborhood of my question / concern.

I have disabled (hidden) the Backup and Backup Wizard icons in all customer cPanels because of the fact that I have WHM set to run a nightly backup (to secondary hard drive in each server), and I'm concerned about users deciding to run their own Backup from cPanel at the same time that WHM nightly backups are already running from main disk to second disk.

Obviously the nightly backup puts forth I/O load spike during that time all by itself, so the main question for me is:

How safe is it to re-enable the Backup icons in cPanel for my customers, knowing that some of them with large accounts will tend to run their own Backup from cPanel at the same time while WHM is running it's nightly backups of their account at the same time?

My secondary question to that would be; if I do enable to Backup icons and a large account user decides to run a full backup of their account while WHM is already in the process of backing up their account to the second drive, does WHM/cPanel already know how to intuitively balance that out or can that scenario cause a potential serious problem (in addition I/O "spike and crawl") , or is there a better way to avoid the clash between the two?

I'm really sorry for the long question but I don't know how to put it into better words.

Thanks for the Webinar this morning, greatly appreciated!

[mario-cPanel]

We appreciate all the questions that are coming in, we will also be posting the recording of the webinar along with presentation slides to the webinar section

We will be working on getting through your questions asap, keep the questions coming in.

[cPanelDavidG]

How can we limit PHP Memory usage. Some scripts create a loop and eat up servers memory which causes swap and eventually high server load.

PHP offers a means of limiting how much memory can be consumed via the memory_limit setting that can be accessed via WHM's PHP Configuration Editor (WHM -> Service Configuration -> PHP Configuration Editor). This is defaulted to 32M.

[cPanelDavidG]

I've had some in-depth discussions this week about using cloudlinux (cloudlinux.com) to limit resources on a per account basis (almost like a VPS but at a cPanel account level). Is this recommended or do you have any views on it?

Specifically this would be to stop one users processes overloading the system?

At this time, we do not yet support CloudLinux (a CentOS-based distribution). You can view a list of supported distros at System Requirements - cPanel Inc. - as a result, we do not currently recommend CloudLinux. However, many of our customers do use CloudLinux, including its ability to limit a user's ability to consume server resources, successfully with cPanel/WHM.

[cPanelDavidG]

Regarding a high WA, would spread accounts on additional disk reduce the server load?

High WA essentially reflects that processes are waiting to use some Input/Output (IO) resource. Almost always on a web hosting server this will be the Hard Disk, the slowest IO resource on a contemporary server.

There are scenarios where spreading accounts across multiple disks would reduce IO wait, and others where it would not. This is why analysis of the processes or scripts causing the high IO wait is important.

For example, if there are many scripts reading a flat-file database contained within their home directory, then having multiple home mount points across multiple physical hard disks can reduce load caused by IO wait since you're essentially spreading the IO requests across multiple physical disks.

However, if IO wait is being caused by reading data from a centralized resource like the Mailman archives on /usr or MySQL databases on /var, then having multiple home mount points does nothing to alleviate the situation since the IO wait is not being caused by anything reading from or writing to the home mount points.

[cPanelDavidG]

Is there a way to create a limited CPanel user, with access only to email and ftp accounts but not to databases and content?

You can remove functionality of the cPanel interface from specific cPanel users by using Feature Manager. First, go to WHM -> Packages -> Feature Manager and create a new "Feature List." Then edit your Feature List, unchecking anything you do not want to offer (e.g. the MySQL icons). You can then apply this to an existing hosting package by editing it, or create a new hosting package and setting the "Feature List" setting for that package to be the Feature List you created. You would then assign this package to the cPanel user.

The WHM interface does not provide a means of assigning a Feature List directly to a cPanel user, that is why the Feature List must be assigned to a Package, then a Package assigned to that user.

[daniel_onnet]

If it's allright with you, I'll break this out into it's own thread and respond to this in a day or so; it's a pretty in-depth question (and a good one). Thanks!

I am fine by it. Go ahead. However, please advice the new thread and where to find it in this forum as I am new here. Thanks.