---
title: "Parallel processing unit limits"
canonical_url: "https://www.zone.eu/support/kb/parallel-processing-unit-limits/"
post_type: "ht_kb"
published: "2024-04-11T10:53:29+00:00"
modified: "2024-10-03T12:27:49+00:00"
language: "en"
author: "silver"
taxonomies:
  ht_kb_category:
    - name: "Apache"
      url: "https://www.zone.eu/support/kb-categories/apache-en/"
    - name: "Technical"
      url: "https://www.zone.eu/support/kb-categories/technical-en/"
  ht_kb_tag:
    - name: "429 error"
      url: "https://www.zone.eu/support/kb-tags/429-error/"
    - name: "503 error"
      url: "https://www.zone.eu/support/kb-tags/503-error/"
    - name: "parallel processing unit"
      url: "https://www.zone.eu/support/kb-tags/parallel-processing-unit/"
    - name: "ppu"
      url: "https://www.zone.eu/support/kb-tags/ppu/"
    - name: "Service Temporarily Unavailable"
      url: "https://www.zone.eu/support/kb-tags/service-temporarily-unavailable/"
    - name: "Too many requests"
      url: "https://www.zone.eu/support/kb-tags/too-many-requests/"
---

# Parallel processing unit limits

### What is a parallel processing unit?

[Web hosting packages](https://www.zone.eu/web-hosting/) have a limit on the number of parallel units that can be used to ensure the stable operation of the shared environment, so that no action taken by one host affects the others.

 The parallel unit shows how many concurrent requests can be made against your web server.

The limit of parallel units depends on the web hosting package, which is listed on our website under the [Resources](https://www.zone.eu/web-hosting/).
In the logs, the entries of the parallel processing units can be found under the **Zunami** name. You can also check the limit of the package in use at the end of the log line, for example **(115/100)**.

### **ZunamiSoftRequestLimit**

The number of connections allowed, above which activity is logged to the Apache log, but requests are not yet rejected and the next log entry remains:

`[2024-01-01 00:00:00.000000] [vhost: domain.eu] [zunami:error] [pid: 12345] mod_zunami.c(341): [client: 123.123.123.123:12345] ZunamiSoftRequestLimit exceeded for 123456 (115/100)`

### **ZunamiHardRequestLimit**

Number of connections allowed before they are rejected. When the given limit is reached, an error message “**503 – Service Temporarily Unavailable**” is returned for the request and the following entry is left in the log:

` [2024-01-01 00:00:00.000000] [vhost: domain.eu] [zunami:error] [pid: 12345] [client: 123.123.123.123:12345] ZunamiHardRequestLimit exceeded for 123456 (170/150)`

 Useful information There is no limit on the number of parallel units on the [Managed CloudServer](https://www.zone.eu/managed-cloudserver/).

### **ZunamiIpConnVHostsLimit**

In addition to the parallel processing units, ZunamiIpConnVHostsLimit entries can also be found in the logs. These represent the number of stack hosts, i.e. the number of main and subdomains on the web server that are allowed to connect to simultaneously. This limit is 10 regardless of the web hosting package.

Requests that exceed the limit will receive a “**429 – Too many requests**” error message and the following entry will be left in the log:

`[2024-01-01 00:00:00.000000] [vhost: domain.eu] [zunami:error] [pid: 12345] [client: 123.123.123.123:12345] ZunamiIpConnVHostsLimit exceeded for 123.123.123.123 (11/10)`

This example shows that connections have been attempted against 11 different hosts on the web server **(11/10)**.