| The Storage Architectural Landscape -
Storage devices now comprise more of the total enterprise IT budget than servers. -
SANs and NAS provide networked storage options and are complementary. -
New IP SANs allow geographic freedom through reach of IP networks. 2.1 Storage Building Blocks -
Basic building blocks include operating systems, file systems, volume management, and storage devices (disks and LUNs). -
SNIA shared storage model helps outline a variety of storage architectures on a single framework. -
SNIA shared storage model helps IT professionals plan for corporatewide storage solutions, enabling greater efficiency. 2.2 Internal Storage/Server-based storage 2.3 External Storage (JBOD, RAID, Tape, Optical, Other) -
JBODs are just what the name says and require additional functionality in the host or network to be scalable and highly available. -
RAIDs enhance performance through striping and provide fault tolerance through mirroring and parity checks. -
Combinations of RAID levels provide mission-critical storage availability to servers and applications. -
Tape drives and libraries provide lower cost per megabyte than disk, but require more time for backup and retrieval. -
Optical storage provides cost in between disk and tape with more resilient media than tape. -
Solid-stage storage is used in niche, high-performance configurations. 2.4 Direct-Attached Storage -
DAS extends server life by providing additional storage capacity. -
DAS can offload some server-based storage functions to the device, such as RAID. -
DAS has high performance but does not scale, offers limited sharing, and can represent a single point of failure. 2.5 Network-Attached Storage -
NAS delivers networked storage but at the file layer, representing a higher level of abstraction. -
NAS uses TCP/IP networks for connectivity. -
NAS works well for file- related applications like corporate file sharing and Web serving, but cannot deliver the performance and scalability for block-oriented applications like databases. 2.6 Storage Area Networks -
SANs deliver the performance and block access of DAS with the network flexibility of NAS. -
First-generation SANs were built with Fibre Channel and delivered gigabit performance, additional scalability, resource sharing, and distances to tens of kilometers. -
Fibre Channel has interoperability between end systems (servers and storage devices), but multivendor switch interoperability is still awkward . -
Pure IP SANs using iSCSI take advantage of longstanding IP and Ethernet networks. -
New IP storage adapters combine the best of traditional IP networking cards with Fibre Channel HBAs to deliver TCP/IP offload for high throughput of IP storage. -
IP SANs deliver unified management, common technology with corporate networks, ability to use trained personnel, and built-in extension to MANs and WANs. -
IP SANs require multiprotocol capabilities to integrate with existing Fibre Channel infrastructure. -
IP storage switches and gateways integrate Fibre Channel storage and Fibre Channel SANs with IP networks. -
IP storage switches and gateways provide conversion capabilities between iSCSI and Fibre Channel for unified, multiprotocol SANs. 2.7 IP SAN Protocols -
The three IP storage transport protocols are iSCSI, iFCP, and FCIP. -
iSCSI and iFCP are IP strategies for supplementing or replacing Fibre Channel fabrics with IP and Ethernet infrastructures . -
FCIP is a Fibre Channel perpetuation strategy to connect Fibre Channel fabrics over distance. -
Multiple protocols are required because iSCSI makes no provision for Fibre Channel. -
Fibre Channel-to-Fibre Channel communication is handled by either the iFCP or FCIP protocols. -
Using iSCSI to link two Fibre Channel systems can result in lost states and poor error recovery. |