ZNC Memory Usage

This page is intended to give users an idea and rough estimate of how much memory ZNC needs to run. Other users are asked to provide anecdotal reports which include memory usage as well as other relevant information.

Various factors can affect ZNC memory usage, including:

• Number of channels (across all users on a ZNC instance)
• Average saved buffer size of each channel
• Whether the AutoClearChanBuffer setting is used. Note that when it's enabled, the configured buffer size can be confusing, because the real buffer size is often zero.
• Query Buffers (if ZNC 1.5 or later)
• Loaded modules (number, type, and function)
• Number of users
• System architecture (x86, x86-64, etc.)

Note: These are anecdotal reports, which are personal experiences of other ZNC users/administrators. These reports are not in any way verified, nor are any of them the least bit scientific. If exact resource usage figures are important, performing your own testing is highly recommended. As always, YMMV.

The following list doesn't include a list of modules used in each case for the sake of brevity. However, module use could have a meaningful effect on memory usage.

There are multiple ways of determining memory usage, but here is the method used for more than half of the entries listed:

$ ps aux --sort -rss | grep znc | awk '{print $1" "$2" "$6}' | column -t

Example output:

zero-one  903    32144
darthga+  18346  5848
zero-one  15469  4652
mindy     1467   1652
hammy     1478   1560

This is the username who owns the process, followed by the PID, and the resident memory usage in kiloBytes.

ZNC Version	Memory Usage	Number of channels	Number of networks	Average Buffer Size	AutoClearChanBuffer	Number of Users	System Arch
1.4	60.9 MB	About 260		About 2,000	Yes, mostly	9	x86-64 (Debian 7.7)
1.4	27.8 MB	About 100		About 100	Yes, mostly	8	x86-64 (Debian 7.7)
1.5	12.1 MB	About 20	4	About 850,000	Yes	1	x86-64 (Slackware 14.1)
1.5	7.3 MB	About 30	2	About 4,290,032,704	Yes	4	x86-64 (Ubuntu 13.10)
1.6.5	160 MB	About 100	5	50	Yes	1	x86-64 (Debian 8)
1.6.5	57 MB	About 100	2	50	Yes	2	x86-64 (Debian 8)
1.7.x-git*	324.75 MB	Over 200		About 50 - 100	Yes	57	x86-64 (Ubuntu 17.04)
1.7.x-git	50.2 MB	53	2	About 1,000,000	Yes	2	x86-64 (Ubuntu 14.04.5 LTS)
1.7.x-git [ZNC-Linker bot]	7.9 MB	2	1	About 50	Yes	1	x86-64 (Ubuntu 14.04.5 LTS)
1.7.x-git	4.7 MB	9	1	About 500	Yes	1	x86-64 (Ubuntu 14.04.5 LTS)
1.7.x-git	10.3 MB	10	1	About 50	Yes	1	x86-64 (Ubuntu 16.04.2 LTS)
1.7.x-git	7.7 MB	7	1	About 50	Yes	1	x86-64 (Ubuntu 16.04.2 LTS)
1.6.5*	250 MB	160	30	About 50	Yes, mostly	30	x86-64 (FreeBSD 10)
1.6.x-git	72.1 MB	566	68	About 2,000 on most channels, 50 on about a third of them.	Yes, mostly	6	x86-64 (Debian 7.11)
1.6.4	41 MB	110	22	300	No	1	x86-64 (openSUSE Leap 42.3)
1.7.x-git	30 MB	31	10	50	Yes	2	x86-64 (Arch)
1.6.5	48 MB	82	11	1500	No	1	x86-64 (Debian 9.3)
1.6.5	20.68 MB	12	5	112.5	No	1	x86-64 (CentOS 7)
1.8.x-git	145.7 MB	276	10	About 500,000	Yes	2	x86-64 (Ubuntu 14.04.5 LTS)
1.7.1	703.4 MB	4354	693	About 100	Yes, mostly	433	x86-64 (Arch)
1.6.5	20 MB	25	4	5000	No	1	x86-64 (FreeBSD 11)

Versions with " * " are modified versions.