| XEN and OPENVZ [message #875] |
Mon, 28 August 2006 07:58  |
 jhamon 
Messages: 357
Registered: May 2006 |
Master |
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Hi,
Can you explain briefly the advantages and disadvantages of these two systems.
Briefly what are the differences between them?
Jonathan Hamon
Jonathan Hamon
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[Updated on: Wed, 30 August 2006 18:31] by Moderator Report message to a moderator |
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| Re: XEN and OPENVZ [message #882 is a reply to message #875] |
Mon, 28 August 2006 08:20  |
Lxhelp
Messages: 23691
Registered: July 2006 |
The Champion |
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| Quote: |
>
>
> Hi,
>
> Can you explain briefly the advantages and disadvantages of these two systems.
>
> Briefly what are the differences between them?
>
>
> Jonathan Hamon
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The primary differences that YOU have to be aware of is this:
OpenVZ:
Advantages: allows overselling. Very light weight. Can accommodate more Virtual Machines in a server.
Disadvantage: There is no per vps swap.
Why this is important:
OpenVZ will KILL your application if it goes beyond the limit, and this can cause some trouble. There are people out there who want to host oracle on a 64MB vps, and with such customers, using openVZ will lead to constant application crashes, which ultimately will be blamed on the provider. (This is actually something that is common with openvz/virtuozzo hosting in general; you can check some threads at wht).
With Xen, each vps has its own swap, and thus you get an EXACT dedicated server like environment, but with lesser resources. So here, the customers applications will NOT crash, but rather it will become slower. Also, majority of the applications, like apache, spamassassin expects a lot of memory, and openVZ makes memory a very valuable commodity.
So generally my recommendation is that: For friendly customers use openVZ, and use a lot of burst memory. For not-so-friendly customers, use Xen. And that is why we are providing transparent migration. You can start a customer on openVZ, and see how it works out, and if he is getting too many application crashes, you can move him to the SAME configuration on Xen, and he should be able to do fine, though his application would be slower.
--
:: Lxhelp :: lxhelp.at.lxlabs.com :: http://lxlabs.com ::
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| Re: XEN and OPENVZ [message #980 is a reply to message #979] |
Sun, 03 September 2006 09:13 |
Lxhelp
Messages: 23691
Registered: July 2006 |
The Champion |
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| Quote: |
> The stability that's offered with guaranteed ram when using Xen in a production environment is very appealing, where the 'wait and see' approach to ram when using OpenVZ isn't necessarily going to be appropriate with some customers, especially where ram related downtime/troubleshooting issues (which can be intermittent) may be unacceptable to the customer.
>
> What I've yet to see is any fair comparisons performance wise between the two platforms where someone has taken a server, installed OpenVZ and created a single VPS to benchmark without having to contend with other users, and then set up the same machine with Xen and done the same thing to compare the results.
>
> I understand that the performance of a VPS running under Xen is below that of an OpenVZ VPS due to the different way in which they are virtualised, but is there any indication as to what kind of performance hit the Xen implentation causes ?
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This is the first task in our todo list. The xen people seems to be always comparing themselves to vmware, which enables them to claim 10 fold improvement in the speed, and ignores the OS level virtualization altogether. We will publish detailed reports on the exact number of VMs possible with each of the technologies. We can make a knowledgeable guess from the overheads claimed by both the virtualizations. For openvz it is 1-2%, while Xen claims an overhead of 1-2% average and 8% in some worst case scenarios, so we can average it to say 3-5%. Xen 3.0 in paravirtualized mode, you should actually get performances comparable to OS level virtualization. Strangely, the openvz folks also haven't published any concrete benchmarks regarding the comparisons.
Theoretically the overheads with Xen would be really minimal since the guest kernel is fully aware of its virtualized status, and I think as the time passes, we will get better and better performances from Xen.
Thanks.
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| Re: XEN and OPENVZ [message #1433 is a reply to message #1432] |
Sat, 23 September 2006 17:41 |
Lxhelp
Messages: 23691
Registered: July 2006 |
The Champion |
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| Quote: |
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> If i want to switch a server over to xen from openvz (new server has 0 vps on it) do i just remove and reinstall with the xen master.sh?
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No need to remove. Just reexecute the master with --virtualization-type=xen. It will say hyperMV is already installed, but you can just type 'yes' there.
Thanks.
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| Re: XEN and OPENVZ [message #2192 is a reply to message #875] |
Wed, 29 November 2006 12:51 |
CleberDantas 
Messages: 149
Registered: October 2006 |
Valuable Member |
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Hello,
I have the hardware with 3GB RAM. I have 6 VMs and each VM uses 500MB RAM. I am having crash in the VM and is killing processes.
Which the instability of the XEN?
Reason the XEN is not stable?
Waiting and reply!
[Updated on: Wed, 29 November 2006 12:52] Report message to a moderator |
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| Re: XEN and OPENVZ [message #2194 is a reply to message #2192] |
Wed, 29 November 2006 21:51 |
Lxhelp
Messages: 23691
Registered: July 2006 |
The Champion |
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Please give higher burst memory. Ask the customer to upgrade. Xen does have some issues still. We will officially announce it, when it is stable.
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| Re: XEN and OPENVZ [message #49916 is a reply to message #49914] |
Wed, 10 December 2008 11:49 |
Lxhelp
Messages: 23691
Registered: July 2006 |
The Champion |
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You can't oversell with xen, but yes, Xen is EXACTLY like dedicated, with its own kernel.
On Wed, Dec 10, 2008 at 04:47:45PM -0000, Eric James wrote:
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> Does XEN provide for unique iptables within each VPS ?
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> Also can you oversell with XEN ?
> ie. if you have 10GB of ram and setup 10VPS each with bursts that actually total more than 10GB aggregate ? Will it allow this or will it limit all VPS's to the actual total of real resources the HN has ?
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| Re: XEN and OPENVZ [message #49924 is a reply to message #49921] |
Wed, 10 December 2008 11:58 |
Lxhelp
Messages: 23691
Registered: July 2006 |
The Champion |
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Each vps has its own swap. But yes, you can't oversell. Neither harddisk nor memory.
On Wed, Dec 10, 2008 at 04:54:31PM -0000, Eric James wrote:
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> Does this also apply to HN swap space or can each VPS have it's own swap within the VPS or is swap tied back to the HN's hard swap space partition ?
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| Re: XEN and OPENVZ [message #49952 is a reply to message #49925] |
Wed, 10 December 2008 14:13 |
Lxhelp
Messages: 23691
Registered: July 2006 |
The Champion |
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| Quote: |
On Wed, Dec 10, 2008 at 05:10:50PM -0000, Eric James wrote:
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> Just so I'm crystal clear...
>
> #1)
> On XEN, if you have a HN with 10GB's Ram and 100GB storage the max you would be able to setup would be something like:
> 10 VPS's each with 1GB RAM and 10GB storage ?
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Yes.
| Quote: |
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> #2)
> In the above example can the VPS have any amount desired of that 10GB's setup as VPS swap ? ie. 8GB's storage and 2GB swap ?
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Yes.
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> #3)
> How much does the HN system reserve for it's own resources that can't be allotted to VPS ?
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HN needs around 512MB or ram.
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| Re: XEN and OPENVZ [message #84916 is a reply to message #82652] |
Thu, 09 June 2011 04:33 |
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For openvz it is 1-2%, while Xen claims an overhead of 1-2% average and 8% in some worst case scenarios, so we can average it to say 3-5%. Xen 3.0 in paravirtualized mode, you should actually get performances comparable to OS level virtualization. Strangely, the openvz folks also haven't published any concrete benchmarks regarding the comparisons
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| Re: XEN and OPENVZ [message #89082 is a reply to message #84924] |
Fri, 16 September 2011 00:31 |
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HI
i am using openvz on hyeprvm.can i know is this posible to install xen alos in the same hyeprvm? can you provide me some suggestions?
Thanks
Vijay
vijaygadde
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