Each host should be configured to accept connections only from well-known entities such as the CloudStack Management Server or your network monitoring software.

Use multiple clusters per pod if you need to achieve a certain switch density.

Primary storage mountpoints or LUNs should not exceed 6 TB in size. It is better to have multiple smaller primary storage elements per cluster than one large one.

When exporting shares on primary storage, avoid data loss by restricting the range of IP addresses that can access the storage. See "Linux NFS on Local Disks and DAS" or "Linux NFS on iSCSI".

NIC bonding is straightforward to implement and provides increased reliability.

10G networks are generally recommended for storage access when larger servers that can support relatively more VMs are used.

Host capacity should generally be modeled in terms of RAM for the guests. Storage and CPU may be overprovisioned. RAM may not. RAM is usually the limiting factor in capacity designs.

(XenServer) 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 http://support.citrix.com/article/CTX126531. The article refers to XenServer 5.6, but the same information applies to XenServer 6.0.