Host-based virtualization can be implemented through a logical volume management (LVM) application installed on each server. As with other solutions, the host-based virtualization application hides the complexity of physical storage while presenting a logical view of storage resources to the operating system. Because the abstraction of physical storage occurs within the server itself, there is no splitting of control and data paths (and in fact no "path" per se). Host-based virtualization bypasses the bottleneck and performance issues associated with in-band virtualization. The host can be multipathed to shared storage, with any mix of storage target devices at its disposal, as illustrated in Figure 11-6. Figure 11-6. Host-based storage virtualizationThe major drawback of host-based virtualization is that virtualization on each host must be manually configured and managed separately. The more servers, the more administrative overhead this imposes. In addition, connectivity to the SAN and individual targets must also be configured on a server-by-server basis. For shops with small server farms, this level of administration may be acceptable, but then with few servers and storage targets there is less incentive to deploy virtualization in the first place. |