Web Hosting Talk : Web Hosting Main Forums : VPS Hosting : Xen or Virtuozzo?

[Funkadelic]

We're currently using virtuozzo and have been but we are thinking of starting a Xen server as our techs have the technical expertise to manage a Xen server. I'm just wondering whether we would be better off with this or not, compared to Virtuozzo. What do you guys think?

[Nick Charlton]

From what I understand Virtuozzo/OpenVZ can be quite weak when it is oversold, whereas with Xen you cannot do this. It all depends on how you are going to implement it, if you are going to install a control panel, admin will be easy once it is setup.

As I haven't used either products, I wouldn't take this as being entirely true, but this is what I have seen, at least.

[nice-price]

@Funkadelic: What do you want to use it for?

[Phrost]

Generally Xen is much more versatile, when oversold Xen will typically give much better performance as it's memory resources are dedicated vs shared on VZ (OpenVZ/Virtuozzo). Xen usually has better CPU performance under high load as the bare-metal hypervisor will handle all of the scheduling vs the VZ kernel scheduler.

Pro's and Con's of each:

Xen:
+ Dedicated memory
+ Dedicated swap
+ Better feature set depending on kernel used (VPN/Tunneling/IPv6)
+ Supports Intel VT (Can run Windows guests with appropriate hardware)
+ High CPU performance, virtual SMP supported for guest VMs
+ Supports NetBSD / Solaris in paravirtual (native) guest
+ Guest support for SELinux/MAC frameworks (depending on kernel)
- Requires dedicated RAM for each VM
- More expensive to host
- Requires dedicated hard drive space for each VM
- Lower I/O performance due to paravirtualization
-- Much lower I/O performance in full virtualization (Windows Guests)
- Longer provisioning / setup times due to custom image creation
- More difficult to backup (pretty much requires LVM snapshots for on-demand backup)

VZ:
+ Very low overhead hosting per VM
+ Allows massive overselling due to shared RAM/Disk space, much cheaper to host / lower prices for the end user
+ Near native performance for high I/O loads (Disk/Net)
+ Much easier to setup/backup
- Starts killing processes when out of RAM (no swap)
- Tends not to allow custom things like VPN/Virutal devices without explicit support from your hosting provider

[devonblzx]

There was just a study done by the university of Michigan, VZ/OpenVZ outperforms Xen greatly in the virtualization. As long as the host does not oversell, VZ will perform better. However, if your client needs things such as their own kernel then Xen will be better but the overhead is much greater.

As for the VPN/virtual devices, it is quite easy for the provider to allow this with VZ, it only requires ~3 ssh commands so I wouldn't necessarily call it "explicit" support.

Also another big thing your forgetting is burstable ram with VZ, yes there is no swap, but burstable ram can be much better because of the speed differences between ram and swap.

[PCS-Chris]

The main thing I prefer about Xen is that fact that no single VM has any impact on the performance of others.

If you have one VM on a Xen Node maxing out CPU/Under high load it has no impact on other VMs on that node.

With Virtuozzo/Container based Virtualization as opposed to Virtual Machines, one user who is using resources such as CPU heavily slows things down for everyone - Even when its "Equal" share.

OpenVZ does provide better performance yes, but generally people go with Xen just for the fact they know it can't be oversold and like I said, no single VM will negativley affect the performance of others.

Burst Ram isnt guaranteed to be available even if the Node isnt oversold, and it can cause instability if you rely on it. A Xen VM might slow down, but youve got that added benefit that it will not kill off your processes when you start to use swap. For RAM or resource intensive applications such as Java Apps or even Gameservers, Xen is the better choice.

[devonblzx]

I don't think that is quite accurate. I don't see what Xen has over VZ in that matter. Any VPS could affect a whole system no matter what virtualization technology, that is why it is up to the host to monitor the server.

If a VPS is receiving DDOS's it can lock up the network, if a VPS is dding it can slow down the i/o. You can limit the CPU in VZ just like Xen, I really don't see the differences, maybe you can explain why one VPS won't affect the others in Xen, it is still sharing one system.

[Funkadelic]

We were just exploring other options other then using Virtuozzo since we have to pay for the licenses, it really limits our profit in this sector.

[Nick Charlton]

Originally Posted by Funkadelic

We were just exploring other options other then using Virtuozzo since we have to pay for the licenses, it really limits our profit in this sector.

If you are happy with your current performance of Virtuozzo, then OpenVZ with HyperVM may be a good option.

Nick

[The Universes]

The issue with swap on a Xen VPS though is it can get horribly slow, depending on the disk i/o.

There are definitely customers out there who want a Xen VPS, so offering the choice won't hurt at all.

[blueroomhosting]

I also fail to see how it is possible for one Xen guest to not be able to negatively effect the others. Surely if there is no load on the system a guest should be able to get 100% CPU while it has something to do and it is uncontented. If another guest is busy all the time then they will both only get 50% when they are both busy, so the other guest being busy has had a direct effect.

This is exactly the same with OpenVZ, only with OpenVZ the overhead for dealing with two busy guests is considerably lower. As such I would suggest that OpenVZ offers better protection from other guests, as their business has less impact.

Properly managed burst memory is equivalent to swap, and it can (and quite possibly should) always be available if it is backed by enough swap on the host. There is no reason to ever hit an out-of-memory situation on a properly set up host.

Also, under high load OpenVZ offers much better CPU performance. Xen's hypervisor and Linux's scheduler both sit at equal distances from the bare metal - they are both implemented in software with direct access to the hardware after all. Linux's scheduler has been worked on for decades, and is very good, but the real advantage for OpenVZ here is the amount of work the scheduler has to do. Xen has to do very expensive context switches with entire kernels, OpenVZ does much cheaper context switches with just the processes, and this is why it scales a lot better than Xen can.

Xen's support for other operating systems, custom kernels, modules, the full set of iptables capabilities etc. are all distinct advantages but they do come at a performance cost. The only reason to be wary of OpenVZ is that hosting providers can oversell on critically important resources (some even allocate more guaranteed memory than they have physical RAM for). This is a pitfall that must be carefully worked around as there are many (probably the majority) who do not oversell.

Jim

[InfiniteTech]

Originally Posted by The Universes

The issue with swap on a Xen VPS though is it can get horribly slow, depending on the disk i/o.

There are definitely customers out there who want a Xen VPS, so offering the choice won't hurt at all.

Market need for Xen VPS has increased due to the near saturation of VZ based hosting firms popping up.

--

Node for Xen, requires to start with 8 GB of RAM on a minimum if you as a host would like to make a profit.

[vibrokatana]

I have used xen and virtuozzo based VPS and overall I like the isolation that xen gives. With virtuozzo it can be good with fast response times and good throughput. Other times it will tank and things will seem slooow, have to restart services, etc. I personally think most virtuozzo hosts oversell drastically to try and make a profit, which is just painful to the average consumer.

xen for the most part you know will be stable and you know you are actually getting what you paid for. You can count on actually having the ram and not having processes freeze up or die due to someone else hogging the server. Disk I/O has never been an issue (taring up the entire drive only takes a few seconds) and transfers are stable (950KB/sec-1MB/sec on my 8mbps line).

Of course you can always get a lemon and have either a bad xen or virtuozzo host. Nothing is going to be perfect, each will have their pros and cons, but I have been burned more by virtuozzo (went through 3 providers) before I settled in on xen.

[The Universes]

Originally Posted by vibrokatana

Of course you can always get a lemon and have either a bad xen or virtuozzo host. Nothing is going to be perfect, each will have their pros and cons, but I have been burned more by virtuozzo (went through 3 providers) before I settled in on xen.

Like you said, YMMV
I've had good experiences with VZ based VPS with Steadfast, Rackforce, and a few others. From what I've seen, on a VZ VPS, you pretty much get access to all the cpu cores, making it quick and snappy. I got a Xen VPS to test and its locked to one cpu core, and gets a little overloaded during peak hours.

Is this a common practice for Xen VPS providers, locking it to 1 core?

[ylsy]

Originally Posted by The Universes

Is this a common practice for Xen VPS providers, locking it to 1 core?

I have used half a dozen Xen providers (Unixshell, SliceHost, Linode, GPLHost, Datarealm, VPSLink, etc...) and while I won't say it is a "common practice", many actually do limit you to just one CPU core in the low-end plans.

Then again some VZ hosts also limit you with the cpulimit setting, which I found even more frustrating than having only one fully-burstable CPU core.