The Cisco UCS support storage types are as follows:

Direct-attached storage (DAS): This is the storage available inside a server and is directly connected to the system through the motherboard within a parallel SCSI implementation. DAS is commonly described as captive storage. Devices in a captive storage topology do not have direct access to the storage network and do not support efficient sharing of storage. To access data with DAS, you must go through a front-end network. DAS devices provide little or no mobility to other servers and little scalability.

DAS devices limit file sharing and can be complex to implement and manage. For example, to support data backups, DAS devices require resources on the host and spare disk systems that other systems cannot use. The cost and performance of this storage depend on the disks and RAID controller cards inside the servers. DAS is less expensive and is simple to configure; however, it lacks the scalability, performance, and advanced features provided by high-end storage.

Network-attached storage (NAS): This storage is usually an appliance providing file system access. This storage could be as simple as a Network File System (NFS) or Common Internet File System (CIFS) share available to the servers. Typical NAS devices are cost-effective devices that do not provide very high performance but have very high capacity with some redundancy for reliability. NAS is usually moderately expensive and simple to configure; plus it provides some advanced features. However, it also lacks scalability, performance, and advanced features provided by SAN.

Storage-area network (SAN): A SAN is a specialized high-speed network that attaches servers and storage devices. A SAN allows an any-to-any connection across the network by using interconnect elements, such as switches and directors. It eliminates the traditional dedicated connection between a server and storage, and the concept that the server effectively owns and manages the storage devices. It also eliminates any restriction to the amount of data that a server can access, currently limited by the number of storage devices that are attached to the individual server. Instead, a SAN introduces the flexibility of networking to enable one server or many heterogeneous servers to share a common storage utility. A network might include many storage devices, including disk, tape, and optical storage. Additionally, the storage utility might be located far from the servers that it uses. This type of storage provides maximum reliability, expandability, and performance. The cost of SAN is also very high compared to other storage options. A SAN is the most resilient, highly scalable, and high-performance storage; however, it is also the most expensive and complex to manage.