Splitting Resources Evenly Between OpenVZ VMs With vzsplit
Version 1.0
Author: Falko Timme
This short guide shows how you can split your OpenVZ host resources evenly between multiple virtual machines with the help of vzsplit. vzsplit generates a sample container configuration file with a certain set of system resource control parameters that you can then apply to your virtual machines.
I do not issue any guarantee that this will work for you!
Using vzsplit
Take a look at
man vzsplit
to learn more about its usage.
Now let's assume we want to run 5 virtual machines on the OpenVZ host. We call vzsplit as follows:
vzsplit -n 5 -f max-limits
-n 5 specifies the number of virtual machines.
server1:~# vzsplit -n 5 -f max-limits
The optimal swap space size is 2022 Mb, twice bigger than the RAM size
WARNING: Recommended minimal size of partition holding /var/lib/vz/private/ is 20Gb!
Config /etc/vz/conf/ve-max-limits.conf-sample was created
server1:~#
As you see, this has created the file /etc/vz/conf/ve-max-limits.conf-sample which contains the max. values of the configuration settings for each of the 5 virtual machines. Take a look at that file:
vi /etc/vz/conf/ve-max-limits.conf-sample
# Configuration file generated by vzsplit for 5 containers # on HN with total amount of physical mem 1011 Mb # low memory 883 Mb, swap size 2047 Mb, Max treads 8000 # Resourse commit level 0: # Free resource distribution. Any parameters may be increased # Primary parameters NUMPROC="1600:1600" AVNUMPROC="452:452" NUMTCPSOCK="1600:1600" NUMOTHERSOCK="1600:1600" VMGUARPAGES="135985:2147483647" # Secondary parameters KMEMSIZE="37052743:40758017" TCPSNDBUF="5797314:12350914" TCPRCVBUF="5797314:12350914" OTHERSOCKBUF="2898657:9452257" DGRAMRCVBUF="2898657:2898657" OOMGUARPAGES="135985:2147483647" PRIVVMPAGES="155342:170876" # Auxiliary parameters LOCKEDPAGES="1809:1809" SHMPAGES="15534:15534" PHYSPAGES="0:2147483647" NUMFILE="14464:14464" NUMFLOCK="1000:1100" NUMPTY="160:160" NUMSIGINFO="1024:1024" DCACHESIZE="8088605:8331264" NUMIPTENT="200:200" DISKSPACE="117286:129015" DISKINODES="110065:121072" CPUUNITS="8587" |
As you see, this file does not contain VM-specific settings such as hostname, IP address, name servers, etc.which makes sense because we don't want to overwrite these settings.
Now let's say we want to apply these settings to our VM with the ID 101. This is how we do it:
vzctl set 101 --applyconfig max-limits --save
Afterwards, you can start/restart the VM 101:
vzctl start 101
You might see something like this:
server1:~# vzctl start 101
Starting container ...
vzquota : (warning) block_hard_limit [129115] < block_current_usage [139856]
Container is mounted
Adding IP address(es): 192.168.0.101
bash: line 402: printf: write error: Disk quota exceeded
bash: line 416: printf: write error: Disk quota exceeded
bash: line 421: echo: write error: Disk quota exceeded
bash: line 447: printf: write error: Disk quota exceeded
Setting CPU units: 8587
Configure meminfo: 155342
Set hostname: test.example.com
awk: close failed on file /dev/stdout (Disk quota exceeded)
ERROR: Can't change file /etc/hosts
vzquota : (warning) block_hard_limit [129015] < block_current_usage [139856]
Container start in progress...
server1:~#
For some reason vzsplit has calculated a wrong disk size. You can correct that as follows (this will set a disk size with a soft limit of 10GB and a hard limit of 11GB - adjust this to your needs):
vzctl set 101 --diskspace "10000000:11000000" --save
Then restart the VM:
vzctl restart 101
You can take a look at the new settings for the VM as follows:
vzctl exec 101 cat /proc/user_beancounters
server1:/etc/vz/conf# vzctl exec 101 cat /proc/user_beancounters
Version: 2.5
uid resource held maxheld barrier limit failcnt
101: kmemsize 340278 580635 37052743 40758017 0
lockedpages 0 0 1809 1809 0
privvmpages 796 1655 155342 170876 0
shmpages 0 0 15534 15534 0
dummy 0 0 0 0 0
numproc 5 9 1600 1600 0
physpages 486 1060 0 2147483647 0
vmguarpages 0 0 135985 2147483647 0
oomguarpages 486 1060 135985 2147483647 0
numtcpsock 1 2 1600 1600 0
numflock 1 2 1000 1100 0
numpty 0 1 160 160 0
numsiginfo 0 2 1024 1024 0
tcpsndbuf 8928 0 5797314 12350914 0
tcprcvbuf 16384 0 5797314 12350914 0
othersockbuf 2232 3624 2898657 9452257 0
dgramrcvbuf 0 0 2898657 2898657 0
numothersock 1 3 1600 1600 0
dcachesize 0 0 8088605 8331264 0
numfile 129 193 14464 14464 0
dummy 0 0 0 0 0
dummy 0 0 0 0 0
dummy 0 0 0 0 0
numiptent 10 10 200 200 0
server1:/etc/vz/conf#
The failcnt column is very important, it should contain only zeros; if it doesn't, this means that the vm needs more resources than are currently allocated to the VM.
To find out about the memory allocated to the VM, run
vzctl exec 101 free
server1:~# vzctl exec 101 free
total used free shared buffers cached
Mem: 621368 3268 618100 0 0 0
-/+ buffers/cache: 3268 618100
Swap: 0 0 0
server1:~#
Links
- OpenVZ: http://openvz.org
