User Quotas and Limits in ISPmanager 6: Full Setup Guide

Why user quotas are needed in ISPmanager 6

On a server with several sites or clients, one heavy account can take up all the disk space, memory, or CPU time and bring down the other sites. User quotas in ISPmanager 6 set hard limits for each account: how much disk space, how many sites, databases, and mailboxes it has access to.

Quotas are configured at the billing plan level or individually for a specific user in the "Users → Billing Plans" section. If the panel runs in reseller mode, plans directly affect what a client sees in their own client area — more on this in the article reselling in ISPmanager 6 Business.

Which parameters can be limited

A billing plan offers a fairly wide set of limits.

Besides these limits, process restrictions are configured separately: how many simultaneous PHP handlers and background processes a user is allowed.

How to create a billing plan with quotas

A plan is a set of limits that is later assigned to one or more users.

1. Open "Users → Billing Plans" and click "Create".
2. Enter the plan name and fill in the disk, sites, databases, and mail limits.
3. If needed, limit the number of processes and the amount of RAM per user.
4. Save the plan and assign it to the required accounts in the "Users" section.

Changing limits in an already assigned plan applies immediately to all users on that plan, so edits on a live server should be made carefully.

How to check actual resource usage

Before tightening a quota, it helps to see how much a user actually consumes. Disk usage can be checked right from the console:

du -sh /var/www/user/data

The number of processes and CPU load for a specific user can be assessed using standard monitoring utilities:

ps -u user -o pid,pcpu,pmem,cmd --sort=-pcpu | head

If a user consistently hits the process limit but does not use the full disk quota, it makes sense to raise the process limit specifically, not the overall quota. A 503 error from an exceeded process limit is easy to confuse with a PHP-FPM crash — how to tell them apart is shown in the article logs and error diagnostics in ISPmanager 6.

What happens when a quota is exceeded

System behavior depends on the type of limit.

• Disk overrun — new files stop saving, the site may show write errors.
• Site or database count overrun — the panel simply does not allow creating a new object beyond the limit.
• Process limit overrun — new PHP requests are rejected with a 503 error until a slot frees up.

ISPmanager 6 shows a notification in the user interface as the disk limit approaches, usually at 90% of the quota.

Common mistakes when configuring quotas

Limits that are too strict or too loose are equally harmful to the server.

• A single disk quota for all clients that ignores the difference between a static site and an online store with photos.
• No process limit — one slow PHP script can grab all the free handlers.
• Changing a plan without warning clients — a sudden drop in the limit breaks a working site.

Checklist before configuring quotas: measure the current disk and process usage of a typical client, add a 20-30% margin on top, and only then lock in the limits in the billing plan.