correct the usual typos
Signed-off-by: Nico Schottelius <nico@bento.schottelius.org>
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Nico Schottelius
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@ -12,10 +12,10 @@ article before continuing to read this one.
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## KVM Host configuration
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The KVM hosts are Dell R815 with CentOS 6.x installed. Why Dell? Because they
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offered us a good price/value combination for the boxes. Why CentOS? Historical
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offered a good price/value combination. Why CentOS? Historical
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reasons. The hosts got a minimal set of BIOS tuning to support the VM performance:
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* Enable the usual virtualisation flags (don't forget the IOMMU!)
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* Enable the usual virtualisation flags (don't forget to enable the IOMMU!)
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* Change the power profile to **Maximum Perforamnce**
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Furthermore, as the CentOS kernel is pretty old (2.6.32-279) and
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@ -24,10 +24,11 @@ command line option to enable the IOMMU:
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amd_iommu=on
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Not enabling this option degrades the performance by at least 100%. In our case,
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enabling it dropped the latency of the application by a factor of 10.
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Not enabling this option degrades the performance.
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In our case, enabling it reduced the latency of the
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application running in the VM by a factor of 10.
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One big motivation of the the KVM setup at local.ch is to make the
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One big design consideration of the the KVM setup at local.ch is to make the
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KVM hosts as independent as possible and sensibly fault tolerant. That said,
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VMs are stored on local storage and hosts are always redundantly connected
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to two switches use [LACP](https://en.wikipedia.org/wiki/Link_aggregation).
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@ -118,13 +119,13 @@ The following configuration is used to create the bond0 device:
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SLAVE=yes
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BOOTPROTO=none
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The MTU of the 10G cards has been set to 9000, as the Aristas support
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The MTU of the 10G cards has been set to 9000, as the Arista switches support
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[Jumbo Frames](https://en.wikipedia.org/wiki/Jumbo_frame).
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Every VM is attached to two different networks:
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* PZ: presentation (for general traffic) (10.18x.0.0/22 network)
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* FZ: filerzone (for NFS and database traffic) (10.18x.64.0/22 network)
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* PZ: presentation zone (for general traffic) (10.18x.0.0/22 network)
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* FZ: filer zone (for NFS and database traffic) (10.18x.64.0/22 network)
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Both networks are seperated using the VLAN tags 2 (pz) and 3 (fz), which result
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in **bond0.2** and **bond0.3**:
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@ -137,7 +138,7 @@ in **bond0.2** and **bond0.3**:
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140: bond0.3@bond0: <BROADCAST,MULTICAST,MASTER,UP,LOWER_UP> mtu 9000 qdisc noqueue state UP
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To keep things simple, the two vlan tagged (bonded) interfaces are added to a bridge each,
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to which the VMs are attached later on. The full configuration looks like this:
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to which the VMs are attached later on. The configuration looks like this:
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[root@kvm-hw-inx01 network-scripts]# cat ifcfg-bond0.2
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DEVICE="bond0.2"
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@ -203,8 +204,7 @@ files:
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* vnc: socket to the screen of the VM
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With the exception of monitor, pid and vnc are all files generated by cdist.
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One of the major concerns of this KVM setup is that all hosts have as little
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as possible dependencies. That said, the start script of a VM looks like this:
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The start script of a VM looks like this:
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[root@kvm-hw-inx03 jira-vm-inx01.intra.local.ch]# cat start
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#!/bin/sh
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@ -227,8 +227,10 @@ as possible dependencies. That said, the start script of a VM looks like this:
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-net tap,script=/opt/local.ch/sys/kvm/bin/ifup-fz,downscript=/opt/local.ch/sys/kvm/bin/ifdown,vlan=300 \
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-smp 4
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Most parameter values depend on output of sexy, which uses the cdist type, which in turn
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assembles this start script. The above script may be useful for one or more of my readers,
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Most parameter values depend on output of sexy,
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which uses the cdist type **__localch_kvm_vm**,
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which in turn assembles this start script.
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The above script may be useful for one or more of my readers,
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as it includes a lot of tuning we have done to KVM.
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@ -272,11 +274,10 @@ is pretty simple:
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;;
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As you can see, every VM is started in its own
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[screen](http://www.gnu.org/software/screen/). We decided to go for this approach,
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as screen is sometimes buggy and hangs itself up. This way, we only lose on machine
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on every screen death, not all of them at the same time. Furthermore, screen is usually
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limited to a maximum number of windows it can server.
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When everything went successful, the process output for a virtual machine looks like this:
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[screen](http://www.gnu.org/software/screen/) - so if screen decides to
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hang up, only one VM is affected.
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Furthermore screen supports only a limited number of windows it can server.
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The process listing for a running virtual machine looks like this:
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root 64611 0.0 0.0 118840 852 ? Ss Mar11 0:00 SCREEN -d -m -S binarypool-vm-inx02.intra.local.ch /opt/local.ch/sys/kvm/vm/binarypool-vm-inx02.intra.local.ch/start
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root 64613 0.0 0.0 106092 1180 pts/22 Ss+ Mar11 0:00 /bin/sh /opt/local.ch/sys/kvm/vm/binarypool-vm-inx02.intra.local.ch/start
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