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Re: [Xen-users] Which one to use: Xen HV, Xen Cloud Platform, or Citrix XenServer?
Hiya Eric,
Yep, pooling is very cool, although it requires identical hardware to work, so for a lot of my experiments involving spare heterogeneous hardware, it hasn't been so useful to me. Also running HA on a pool requires a XenServer advanced license (which I must say is reasonably priced, and Citrix certainly deserves support), and also only really works well out-of-the-box with a real shared storage device. Without a shared storage device, I did get HA working on an active/active DRBD setup with XS Advanced, but found it was prone to split brains and just wasn't quite stable enough that I'd trust it with our database VM. My current side project is creating an active/hot standby HA VM using DRBD in active/passive, pacemaker, and XS, which is working really well so far in initial tests with 2 normal XSs and local disks.
So about that XCP Debian thing.. really all that means is it's like you can build your own XCP with Debian as the dom0 instead of CentOS.
XCP (and XenServer which is the same thing, just not open source) is a complete package of a dom0 OS + Xen + XenAPI + other useful stuff.. the idea behind it is that it's a simple bare-metal installable ISO that saves you the trouble of installing your own Linux with all the right packages. It's been tested and will work when installed. This is comparable to ESXi, which is using the VMware hypervisor down underneath all of that management stuff, and it's all packaged up into a nice ISO.
So now for Debian for those who want to use XCP, but really want Debian instead of CentOS as the dom0.. they're saying you can install it all yourself if you like and use Debian as the base. To me that just sounds like a way to introduce a lot of variables and complexity into the install and neatly avoid all the advantages of a tested working pre-packaged system... e.g. not something I'd go install into production without having very carefully tested every part myself first in the lab...only worth it if you need it.
One important thing to understand is that all of these things are using Xen at the bottom, which is the actual Hypervisor. XCP and XenServer are running their VMs on Xen.
When people are talking about XCP like that ("install the XCP package"), mostly what they're talking about is installing XenAPI along with Xen. XenAPI is the API that XenCenter (for example) is using to contact your XCP/XenServer host and do stuff like "get all VMs", "start VM", etc. It's just an API abstraction for managing Xen.
IMHO I think that terminology is confusing and the XCP label should be reserved for reference exclusively to the official installable ISO packaged version, but it's all evolving... and in the above case I think they're using XCP more like a label for any system that's using the same group of packages (e.g. Xen + XenAPI, etc).
Production is best run on stable software... to me that means I'd stick with XenServer today (free edition is a great start), and in the future possibly XCP or your own rolled up version of Xen/XenAPI packages if you have a more complex architecture that needs it.
I haven't used Debian + Xen myself, so will have to defer to others there.
Cheers, Andrew
On Sun, Jul 1, 2012 at 3:30 AM, Eric <epretorious@xxxxxxxxx> wrote:
Thanks for telling me about Remus, Andrew:
Fault-tolerance (FT) on Xen HV/XCP/XS is a topic that I am very curious about but haven't had time to delve into.
I've set up a two node XenServer pool using XenCenter and have been impressed with the simplicity of managing XS using XC.
However, while digging a little deeper into the quesion of Debian and the Xen Hypervisor I discovered that Debian has announced that Debian 7.0 (Wheezy) will also include XCP (1.3)...
...and now I'm really puzzled (because I thought that XCP was a complete hypervisor platform [similar to
VMware ESXi and Citrix XenServer] that included a CentOS-based Dom0). I'm also a bit put-off by, what seems like, the large number of packaging issues related to XAPI in/on Debian. (Is that a fair assesment, in your opinion?)
I do like that Wheezy will ship with Xen Hypervisor 4.1, though, and I like that I'll be able to extend/modify the DomO using the extensive Debian package library (and/or by installing/compiling software from source [e.g., Gluster]).
I haven't tested XCP yet though and I'm wondering what others' experience has been with Debian+Xen? Eric Pretorious Truckee, CA
To: Eric <epretorious@xxxxxxxxx>
Sent: Wednesday, June 27, 2012 6:37 PM
Subject: Re: [Xen-users] Which one to use: Xen HV, Xen Cloud Platform, or Citrix XenServer?
I have to agree with Eric here --
I found it really difficult to determine that type of high-level question when I first got into playing around with Xen, XCP, and XenServer.
Reading through "the docs" doesn't really give you those answers.
There's lot of in-depth information, but not much available that just explains the basics a sys admin would want to know.
Even now after having played with all 3 for a while, I'm not totally confident of the answers to the questions raised by the OP:
- is more stable?
-
has more features? e.g., live migration, high-availability, etc.
-
tracks Xen HV development more closely?
In particular I can't speak for Xen vs XCP/XenServer... but I do feel that XenServer is more stable than XCP as XCP is derived from the XenServer code base and then basically I think has the proprietary bits pulled out (is that right guys?), so overall XenServer certainly must be more stable as it attracts more of Citrix's time and effort in testing and certifying the releases.
I'd be inclined to recommend XenServer to anyone who doesn't need anything more than the free version of XenServer provides.
With that said, we have been using XCP 1.1 on a number of servers here as well and haven't had any issues, so I think it's quite a nice product.
Check out the comparison matrix here:
Note, neither XCP nor the free XenServer will give you HA. For that you need the Advanced Xenserver, and HA can be a bit tricky to setup.... it's not uber obvious from the online docs either, but HA will only work if you have identical server hardware that can be setup in a pool and you also need a shared storage backend (or setup DRBD for shared storage, which we've played with, but I wouldn't recommend to the faint of heart or those who want things to work easily without a lot of messing around).
I'm going to shortly be playing around with the alternative which is to do an active/passive HA DRBD setup using free XenServer and the above guide.
For HA with plain Xen there's also Remus ( http://nss.cs.ubc.ca/remus/), which I haven't tried yet, but really would love to hear from others how well it works.
Cheers, Andrew
Andrew Eross CTO Locatrix Communications
On Wed, Jun 27, 2012 at 5:38 PM, Eric <epretorious@xxxxxxxxx> wrote:
> From: Fajar A. Nugraha <list@xxxxxxxxx>
>To: Eric <epretorious@xxxxxxxxx>
>Cc: "xen-users@xxxxxxxxxxxxx" <xen-users@xxxxxxxxxxxxx>
>Sent: Tuesday, June 26, 2012 5:27 PM
>Subject: Re: [Xen-users] Which one to use: Xen HV, Xen Cloud Platform, or Citrix XenServer?
>
>On Wed, Jun 27, 2012 at 6:01 AM, Eric < epretorious@xxxxxxxxx> wrote:
>> With so many different avenues for using Xen I'm wondering which path to
>> take:
>>
>> Xen Hypervisor (e.g., CentOS 5.x, Debian {4,5,6}, etc),
>> Xen Cloud Platform [XCP], or
>> Citrix XenServer [XS].
>>
>> Is there one platform that...
>> is more stable?
>> has more features? e.g., live migration, high-availability, etc.
>> tracks Xen HV development more closely?
>>
>> Is there one Linux distro that...
>>
>> is more stable than the others?
>> tracks Xen HV development more closely? e.g.,RHEL/CentOS 5.x uses Xen 3.0.
>> Debian 6 uses Xen 4.0 AFAIK.
>
>If you've read the documentations and try some of them, like I
>recommended before, you'd probably know the answer already :)
2. Recommended *before*?
>In short, there's no silver bullet. You can't have it all. For now anyway.
>It's your choice whether to pick appliance-type vs distro-installed,
>and newer-features vs rock-stable-and-proven.
Yeah, I know. That's why I'm asking list members to share their experience and their perspective.
>Going forward, since xapi tools will be available and developed mainly
>on debian/ubuntu, those would probably be the best choice. I wouldn't
>hold my breath though, as (from experience) most likely it'd take
>several years to get there.
Thanks, Fajar. That seems like good advice.
Eric Pretorious
Truckee, CA
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