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How fine virtualization could openvz do? [message #4231] Mon, 03 July 2006 12:05 Go to next message
thepontifex is currently offline  thepontifex
Messages: 5
Registered: June 2006
Junior Member
Hello together,

i read much docs about openvz in the last days and i test it currently with fedora c4 on the VE0 and fedora c5 at the ve's.
My hostsystem is an AMD 64 3800+ with 2GB RAM and 40 GB harddisk memory.

I read about the scalability of the VE's but one point is not clear for me:

Is it possible to simulate a specific hardware layout, for example each VE is a 100MHz CPU with 32 MB RAM and 1000 MB disk space?

The diskspace is no problem, for that i could use quota, but the rest?

Greetz
Frank


Frank
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Re: How fine virtualization could openvz do? [message #4233 is a reply to message #4231] Mon, 03 July 2006 12:19 Go to previous messageGo to next message
kir is currently offline  kir
Messages: 1645
Registered: August 2005
Location: Moscow, Russia
Senior Member

For the CPU side, you assign different cpuunits values to different VEs, and they get their CPU shares according to their cpuunits. That means a VE can have up to 100% of the CPU if nobody else is using it; in case more than one VE is using a CPU, CPU time will be distributed in proportions to VE's cpuunits.

In case you want to have an upper limit on the CPU time a VE can have, use cpulimit option. But this is not really needed, since OpenVZ CPU scheduler is "fair" ... so the only time you need this cpulimit is when you want to simulate a slow machine or smth like this.

For the RAM side, it is not that straightforward, since RAM is used for a lot of different tasks. In short, RAM available for a VE is regulated by a set of so called User Beancounters. For more info, search this forum for user beancounters (or UBC), read OpenVZ user's guide, and check http://wiki.openvz.org/Resource_management


Kir Kolyshkin
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Re: How fine virtualization could openvz do? [message #4236 is a reply to message #4233] Mon, 03 July 2006 15:19 Go to previous messageGo to next message
thepontifex is currently offline  thepontifex
Messages: 5
Registered: June 2006
Junior Member
Quote:

In case you want to have an upper limit on the CPU time a VE can have, use cpulimit option. But this is not really needed, since OpenVZ CPU scheduler is "fair" ... so the only time you need this cpulimit is when you want to simulate a slow machine or smth like this.


Yes, but thats the point I want to know: can I use openvz to virtualize for example 5 slow mashine with 100 MHz cpu power and 32 MB RAM. I need an environment with mostly equal mashines, to simulate something. The number of mashines could be 5 or goes up to 100 so a hardware solution is not possible. Here comes the chance of openvz.

Regards
Frank


Frank
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Re: How fine virtualization could openvz do? [message #4237 is a reply to message #4236] Mon, 03 July 2006 15:43 Go to previous messageGo to next message
kir is currently offline  kir
Messages: 1645
Registered: August 2005
Location: Moscow, Russia
Senior Member

Yep, that could easily be done. By default all VEs have equal configurations and resource management params. Depending on the hardware, you can have up to several hundred "light" VEs on a single server.

Kir Kolyshkin
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Re: How fine virtualization could openvz do? [message #4238 is a reply to message #4237] Mon, 03 July 2006 15:59 Go to previous messageGo to next message
thepontifex is currently offline  thepontifex
Messages: 5
Registered: June 2006
Junior Member
Quote:

Depending on the hardware, you can have up to several hundred "light" VEs on a single server.


OK, but I only read about cpu time units or cpu time in percent. But how can I determine that the VE CPU has 100 MHz and not more. Or must I calculate:
Host 3800 MHz => 100 MHz = 2,631% cputime?

I don't think thats right?!

Greetz
Frank



Frank
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Re: How fine virtualization could openvz do? [message #4239 is a reply to message #4238] Mon, 03 July 2006 16:01 Go to previous message
kir is currently offline  kir
Messages: 1645
Registered: August 2005
Location: Moscow, Russia
Senior Member

You are totally right. Just note that if a server has more than one CPU, total value is more than 100% (say, 400% in case of 4-CPU box).

Kir Kolyshkin
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