On Mon, Jul 26, 2010 at 2:03 PM, Gilberto Nunes gilberto.nunes32@gmail.com wrote:

Hi Victor... Me too!... When the year started, I installed a server with Xen 4.0, with 2.6.31.13 pvops kernel We have 15 VM on a Dell PowerEdge 1950 with 16 GB of memory and SAS disks... This sound like crazy thing I know that... All VM runs Windows 2003 Servers... Now I see that the performance on VM has decrease so much... Perhaps I would change to KVM from xen???

What you thing about???

2010/7/26 Victor Padro vpadro@gmail.com:

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On Mon, Jul 26, 2010 at 1:30 PM, Gilberto Nunes gilberto.nunes32@gmail.com wrote:

...

Friends I'm in doubt here: which virtualization platform to choose and why?

If I have just installed a VM I choose Xen or KVM? And when I have more than 5 or 10 VM's?

Please, I need your help to choose right.

Thanks

Gilberto Nunes _______________________________________________ CentOS-virt mailing list CentOS-virt@centos.org http://lists.centos.org/mailman/listinfo/centos-virt

It depends on which clients are you going to virtualize, personally I like using KVM for the simplicity to run Windows and Linux guests.

-- Linux User #452368 http://twitter.com/vpadro

"Everything that irritates us about others can lead us to an understanding of ourselves" _______________________________________________ CentOS-virt mailing list CentOS-virt@centos.org http://lists.centos.org/mailman/listinfo/centos-virt

-- Gilberto Nunes _______________________________________________ CentOS-virt mailing list CentOS-virt@centos.org http://lists.centos.org/mailman/listinfo/centos-virt

Perhaps you could run a test lab with the same VMs under KVM, but I can assure you performance will not be overkill, just 5-7% more, nevertheless KVM seems to be more stable on my Server Xeon X3440, 8GB, PERC 6, 8TB running 8 Windows 2K3 R2 VMs, it has been running for six months now without downtime.

Saludos.

Hi Eric...

I'm using virtio drivers on my hosts... Both Xen and KVM.

What I see is the KVM has been easier to manage and maitain.

Also, KVM is more easier to implement, 'cause I don't need re-compile the kernel...It's just do a modprobe and everything is well...

Thanks

2010/7/26 Eric Searcy emsearcy@gmail.com:

On Jul 26, 2010, at 12:03 PM, Gilberto Nunes wrote:

[...]

...

What you thing about???

As far as running 15 VMs, whether your hardware is suited to do that depends on how many spindles worth of SAS drives you have (improves concurrency), how busy your VMs are (IO and proc), how much the guests are swapping in case you're not giving them enough memory.  And if you're not running virtio drivers, you should!

I don't have the numbers, but several months ago I tested a few different Iometer meter workloads on Server 2003 R2 guests on PE1950 hardware against equivalently-matched VMs on the 1.x version of a popular proprietary product (dedicated memory instead of its default swap-mem-to-host-disk; also running the guest extensions), Xen on CentOS 5.4 with a then-recent build of GPLPV (meadowcourt.org/downloads) on the guests, and KVM (also CentOS 5.4) with somebody's build of unsigned virtio Windows drivers (was on a /~public_html from redhat.com I think).

Results: Xen+GPLPV beat out KVM+virtio enough to be considered significant, but their difference seemed small compared to the margin they beat the other contender by.  The proprietary one also had massive CPU load on the guest generated by running the test that the others didn't have.

Obviously that's all very vague, but then again I'm sure somewhere I've accepted a EULA that says I'm not allowed to share benchmarking results for certain products :-).

I'll be keeping Xen (and therefore CentOS 5.x) around to run Linux guests blazingly fast on still-usedful hardware.  Everything else I'm (slowly) migrating to KVM in the interest of tracking with upstream.  Xen's slight performance edge on Windows will be missed.

YMMV.

Eric _______________________________________________ CentOS-virt mailing list CentOS-virt@centos.org http://lists.centos.org/mailman/listinfo/centos-virt

Grant McWilliams grantmasterflash@gmail.com writes:

I'm not sure any of the rest of us have ever had to recompile the kernel to get xen to work either. I have 160 or so DomUs on CentOS Dom0s and still haven't recompiled a kernel.

how many guests per dom0? for my smallest plans I approach 160 DomUs per dom0, and I /have/ had to recomplile to make that work. (though, it's been rather a long time since I tried it with a CentOS/xen kernel rather than a xen.org kernel.)

Grant McWilliams grantmasterflash@gmail.com writes:

What kind of situation would you be trying to run 160 DomUs per Dom0? I'd be curious about your particular needs for having that many DomUs per Dom0. Did you run into a hard coded limit on the number of DomUs you could have?

Well, the smallest server that it is economical to buy and run has 32GiB ram. (this /may/ change when the amd 4100 chips come out; I haven't started poking them yet. The numbers certainly /look/ good.) I give 1GiB to the dom0 (a little liberal, yes, but it's cheap insurance, I say)

My smallest plan is 64MiB ram. Now, I don't sell many of those, because for a dollar more a month, I'll give you 128MiB ram, which is /much/ more useful. (I mostly keep the 64MiB plan out of pricing consistency; I charge a dollar a month for every 64MiB ram, and then $4/month for each account for support/abuse overhead.)

so I fill up those 31GiB with 128MiB ram guests, that gives me 248 guests on one server. Even if I didn't sell anything smaller than 256, which is my most popular plan, that'd still be 124 guests, which is more than I've gotten with the stock kernel (with two block and one network device per guest; one disk is a read-only 'rescue' image, accessable via pvgrub, and the other is the customer's disk.)

Now, I put all guests 512MiB ram and smaller on one server, so it's very rare that I go over 150 guests per server outside of testing, but as you can see, I want the option to do so.

If you are interested in the details of what I had to change:

http://book.xen.prgmr.com/mediawiki/index.php/Many_guests

Hi...

How manu guest do you running??

thanks

2010/7/26 compdoc compdoc@hotrodpc.com:

KVM seems to have a future in centos.

I have a couple of servers running kvm, with only 4 cores per server. I tend use 1 real core for each virtual cpu assigned to the guests, because I don't need that many guests. So, I can't speak to scaling...

Performance is excellent, however. It's been a year or more since I've tried ESXi or xen on ubuntu, but I was always disappointed in the speed at which the guests ran.

That's why I turned to xenserver for its speed and GUI, and then to KVM for its speed and complete control over things like nics and network configurations.

KVM works great

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2010/7/26 Pasi Kärkkäinen pasik@iki.fi:

On Mon, Jul 26, 2010 at 03:30:38PM -0300, Gilberto Nunes wrote:

...

Friends I'm in doubt here: which virtualization platform to choose and why?

If I have just installed a VM I choose Xen or KVM? And when I have more than 5 or 10 VM's?

Please, I need your help to choose right.

It depends on many things.

If your hardware doesn't have CPU virtualization extensions, then you only have one choice - Xen.

Yes. All hardware has virt extensions...

If you want to use 32bit host OS, then you only have one choice - Xen.

Yes... All software is 32 bits

And if you run mainly Linux VMs then Xen is a good choice.

No... Mostly software is Windows based here...

-- Pasi

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