Chapter 21. Tuning
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For more information about the buffer pool, see "The InnoDB Buffer Pool" at MySQL Reference
Manual2.
21.4. Set and Monitor Total VM Limits per Host
The CloudPlatform administrator should monitor the total number of VM instances in each cluster,
and disable allocation to the cluster if the total is approaching the maximum that the hypervisor can
handle. Be sure to leave a safety margin to allow for the possibility of one or more hosts failing, which
would increase the VM load on the other hosts as the VMs are automatically redeployed. Consult the
documentation for your chosen hypervisor to find the maximum permitted number of VMs per host,
then use CloudPlatform global configuration settings to set this as the default limit. Monitor the VM
activity in each cluster at all times. Keep the total number of VMs below a safe level that allows for
the occasional host failure. For example, if there are N hosts in the cluster, and you want to allow for
one host in the cluster to be down at any given time, the total number of VM instances you can permit
in the cluster is at most (N-1) * (per-host-limit). Once a cluster reaches this number of VMs, use the
CloudPlatform UI to disable allocation of more VMs to the cluster.
21.5. Configure XenServer dom0 Memory
Configure the XenServer dom0 settings to allocate more memory to dom0. This can enable XenServer
to handle larger numbers of virtual machines. We recommend 2940 MB of RAM for XenServer dom0.
For instructions on how to do this, see Citrix Knowledgebase Article3.The article refers to XenServer
5.6, but the same information applies to XenServer 6
2 http://dev.mysql.com/doc/refman/5.5/en/innodb-buffer-pool.html
3 http://support.citrix.com/article/CTX126531