Here are some tips to improve the performance for KVM guests using the SolusVM management system.
Networking
Currently SolusVM offers three NIC Card options: Realtek 8139, Intel PRO/1000, Virtio.
Intel Pro/1000 should be used for Windows or Ubuntu 12 as it gives best performance for these OSes. Additional drivers may be required, but you can download and install them from intel.com. Also the Intel Pro/1000 supports 1Gbps connectivity.
Virtio is recommended on any OS other than Windows and Ubuntu 12. It also supports 1Gbps connectivity.
Realtek 8139 should be the last alternative in case none of the above are supported. Connectivity for this one is limited to 100Mbps.
I/O Performance
SolusVM gives two alternatives for Disk Driver: IDE and Virtio. Unless your OS requires IDE, you should always choose Virtio for best performance.
Another setting you will see is the Disk Cache. Different caching modes are available: default (default is in fact writethrough), writethrough, writeback, none, directsync, unsafe. For a complete guide, read the following article: A guide to KVM Guest Disk Cache.