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Re: [Xen-users] Please help estimate number of the domUs

Yes, It has 4 NICs and I'm planning to use one for managment and 3 others in bonding as bridge with the open vswitch backend. Also I'm planning to rate limit VMs traffic to 20 Mbit/s so I hope network boundaries will not be reached. I think general purposes of the VMs as VPS will be customer servers and not desktops.


15.01.2013 12:25, J.Witvliet@xxxxxxxxx ÐÐÑÐÑ:
If you try to startup all images at the same time, or when doing very 
disk-intensive jobs, like a compile farm, performance is probably sub-optimal 
Otoh, when all of these machines are used by remote people interactively, your 
lan is probably the weakest link.
If you have the same box as we do, you have four nics, and you will need them 
to spread the load.
You might even consider adding some extra 10Gb nics.

So the number of domU's you can practically use depends of their purpose....
If it is just a bunch of webservers, that people reach once-in-a-while, you 
might reach for the upper limits.
Otoh, if they are used as remote desktops, you will probably be memory/network 
bound, and when acting as compile/crunch farm, you'll be disk bound.


-----Original Message-----
From: xen-users-bounces@xxxxxxxxxxxxx [mailto:xen-users-bounces@xxxxxxxxxxxxx] 
On Behalf Of admin@xxxxxxxxxxx
Sent: Sunday, January 13, 2013 8:52 PM
To: xen-users@xxxxxxxxxxxxx
Subject: Re: [Xen-users] Please help estimate number of the domUs

You should measure the performance of the SAN using something like
IOmeter (running IOmeter on the hardware you plan to run XenServer or
XCP on).  Assuming you configure those drives in RAID10, I would guess
that SAN would deliver about 2,000 to 5,000 IOPS.  If you use RAID5
(please don't), then you will see far less IOPS during mixed read and
write tests.

If you want to deploy 100 VMs onto that SAN, then each VM is only have
to have 20-50 IOPS (assuming RAID10).  The performance in each VM will
be less than fantastic.  If the VMs need to do any IO intensive tasks,
the owners of the VMs are probably going to complain about sluggish
performance.  I don't think the SAN you listed can deliver enough IOPS
to satisfy 100 VMs.

On 1/13/2013 12:17 PM, Andrey wrote:
Well, storage is the direct-connect HP P2000 G3 FC dual-controller
array with 600GBx24 disks in dual-path configuration (two HBA ports ->
two controllers ports). I guess it is quite enough.

13.01.2013 20:45, admin@xxxxxxxxxxx ÐÐÑÐÑ:
You will probably run out of disk IO before you run into any hard limits
in XenServer or XCP.

What type of SAN are you going to use?  What type of network
interconnect will you use to link your XenServer/XCP nodes to your SAN?
How many IOPS does your SAN deliver over your chosen network

On 1/13/2013 9:03 AM, Andrey wrote:
Sure, will try. I see in XenServer 6.1 FAQ that maximum supported
number of guests is 150 and it requires increasing dom0_mem to max
4096. It's obvious that internal limits are not quite realistic so it
will be good result for me if we able to run at least 100 guests. It
seems that it is more realistic number although some resources note
maximum number of VMs as 4-10 per CPU core (so 32-80 in my case). But
in all these cases 192 GB RAM would be redundant I think.

With regards, Andrey

11.01.2013 16:43, Wei Liu ÐÐÑÐÑ:
On Fri, 2013-01-11 at 12:24 +0000, Andrey wrote:
Thank you for the answer

I'm really consider the case with creating as many DomUs as possible
with typical load and get practical info.

What about network capacity? Does this math implies to the network
resources? Should we shape the DomUs bandwidth to prevent network
overload? Can CPU be bottleneck in this configuration?

The math I did was to show you some internal infrastructure limits
I know.

CPU / network overloading is another topic. TBH I haven't done stress
tests on CPUs and network.

And whether you will hit any bottlenecks in CPU / network or not
closely to your use case. Boot up DomUs and do some typical
workload is
a good idea.


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