Re: [Xen-users] How many guests

[Jonathan Tripathy <jonnyt@xxxxxxxxxxx>]

Thanks Micael,

I understand what you are saying.

With a small setup such as a RAID1 array, how many VMs could I rent out?

It doesn't matter if it's a small number, it's just to utilise the 
server a bit.
Think it would cope with 5-10?

Thanks

Jonathan
On 06/06/10 20:18, Michael Schmidt wrote:
> Hi Jonathan,
>
> if you plan to migrate existing physical machines to xen VMs, or you 
> have some different machines for a comparison,
> you can easy get runtime statistics and calculate the usage. Look at 
> the running iostats and cpu usage.
> If you plan to rent generic VMs on this server to customers, you disk 
> / raid setup will be absolutely the bottleneck.
> A solution at this point is not easy. If you have much write IOs, use 
> raid 10 with 4 to 8 disks. With many reads - raid 6 or 50 with the 
> same amount of disks.
> In each case i can suggest you 15k rpm SAS disks.
>
> Then you can run 29 VMs. Or 60 VMs with 16GB memory and 2 CPUs.
>
> But note: You cannot set disk priority to the VMs. So if one VM does 
> heavy disk IO, all off the other VMs slowed down.
> Best Regards
>
> Michael Schmidt
>
>
> Am 06.06.10 20:45, schrieb Jonathan Tripathy:
> > Hi Michael,
> >
> > Thanks for your email.
> >
> > This is just an idea that I have floating around in my head that 
> > maybe I'd like to rent out some VPSs to customers, just to utilise my 
> > machine which will be sitting in a co-lo nearly idle.
> > I'd give out VPSs with 256MB RAM and probably 5Mbps connection speed.
> >
> > So the answer is, I don't know what will be running on them, however 
> > I could write up an "acceptable use policy", as well as use some 
> > throttling/scheduling?
> > Thanks
> >
> > On 06/06/10 19:39, Michael Schmidt wrote:
> > > Hi Jonathan,
> > >
> > > the question is, what a kind of VM?
> > > You can over-utilize a much greater machine with one VM.
> > > Or on the other side, you can run 40 VMs on a shorter machine.
> > >
> > > Each ressource can be a bottleneck
> > >
> > > - Memory - this is realy easy to calculate: Avaiable minus 768MB 
> > > (Reserved for Dom0 should be enugh in this case).
> > > - CPU - Here we need a VM statistic
> > > - Disk Bandwidth - Here we need a VM statistic, but in the most 
> > > cases not the bottleneck
> > > - Disk IOPS - Here we need a VM statistic, in the most cases the 
> > > botelneck
> > > What a kind of VMs you plane to run?
> > > Webservers / mailservers / database-servers ...?
> > >
> > > Best Regards
> > >
> > > Michael Schmidt
> > >
> > >
> > > Am 06.06.10 00:54, schrieb Jonathan Tripathy:
> > > > Hi Everyone,
> > > >
> > > > I have a Dell R210 server which has a Xeon X3430 Quad Core CPU 
> > > > (2.4Ghz x 4) with 8GB of RAM. I intend to use the H200 controller 
> > > > in a RAID1 setup
> > > > How many VMs do you think I'd be able to run on this machine? Is 20 
> > > > pushing it?
> > > > I'd say most (if not all) guests would be in PV mode.
> > > >
> > > > Thanks
> > > >
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