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

[Andrey <basketboy@xxxxx>]

Just finished measuring SAN performance with IOmeter 
(http://vmktree.org/iometer/OpenPerformanceTest.icf and 5 minutes each 
test) on RAID10 (data, 16GB maximum test file) and RAID50 (backup, 8GB 
maximum test file) both 3.6TB with one ext4 partition. SAN is configure 
in dual-path configuration and server has multipath configured with 2 
HBA adapters. Here are the results:
RAID 5+0:
-----------------------------------------------------------------
|       Test name               |   Avg iops    |       AvgMBps |
-----------------------------------------------------------------
| Max Throughput-100%Read       |       47528   |       1485    |
| RealLife-60%Rand-65%Read      |       24760   |       193     |
| Max Throughput-50%Read        |       6959    |       217     |
| Random-8k-70%Read             |       26612   |       207     |
-----------------------------------------------------------------

RAID 1+0:
-----------------------------------------------------------------
|       Test name               |   Avg iops    |       AvgMBps |
-----------------------------------------------------------------
| Max Throughput-100%Read       |       44031   |       1375    |
| RealLife-60%Rand-65%Read      |       49474   |       386     |
| Max Throughput-50%Read        |       43002   |       1343    |
| Random-8k-70%Read             |       49930   |       390     |
-----------------------------------------------------------------

Caching is in action or else?

13.01.2013 23:52, admin@xxxxxxxxxxx ÐÐÑÐÑ:
> 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
> > > interconnect?
> > >
> > > 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
> > > > > that
> > > > > 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
> > > > > relates
> > > > > closely to your use case. Boot up DomUs and do some typical
> > > > > workload is
> > > > > a good idea.
> > > > >
> > > > >
> > > > > Wei.
> > > > _______________________________________________
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> > >
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