Storage access is a crucial configuration for UCS solutions providing raw storage for both virtualized and non-virtualized servers. Most UCS deployments run virtualized environments where virtual workloads leverage many advanced features of centralized storage accessible through FC, FCoE, and iSCSI protocols. Most UCS blade servers provide very limited direct-attached internal storage space sufficient for installing hypervisors locally and leveraging centralized storage for all virtual servers.

Raw storage is available in three different categories. We will now briefly introduce these main raw storage categories:

• Direct-attached storage (DAS): This is the storage available inside a server and is directly connected to the system through the motherboard. The cost and performance of this storage depends upon 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 filesystem access. This storage could be as simple as an NFS or CIFS share available to the servers. Typical NAS devices are cost-effective devices without very high performance but with very high capacity with some redundancy for reliability. NAS is usually moderately expensive, simple to configure, and provides some advanced features; however, it also lacks scalability, performance, and advanced features provided by SAN.
• Storage area network (SAN): This storage provides remote raw block-level storage to the connected servers. This type of storage provides maximum reliability, expandability, and performance. The cost of SAN is also very high compared to the other two storage options. SAN is the most resilient, highly scalable, and high performance storage; however, it is also the most expensive and complex to manage.

FC and iSCSI are the two main protocols for SAN connectivity. FC has its own standards and protocols provided by IEEE whereas iSCSI runs on top of standard Ethernet protocols. Both FC and iSCSI encapsulate Small Computer System Interface (SCSI) protocol commands.

iSCSI storage can be connected either with Fabric Interconnect or through network switches to provide enterprise storage capacity to compute servers. UCS Servers can access the iSCSI storage similar through both software and hardware based iSCSI initiator that can be easily created through service profiles on Cisco VICs.

Alternative options for massive storage requirement can be fulfilled by connecting recently launched Cisco UCS S3260 dual node storage servers to Fabric Interconnect as discussed in the first chapter. Each server is capable of providing 600 TB data storage and can be expanded upto 3 PB with multiple servers connected to it. The S3260 can be best fit for the scale-out storage requirements of any enterprise.