DAS, NAS and SAN

1. DAS, NAS and SAN Ryan Leonard Storage and Solutions Architect

2. Agenda • DAS, NAS, and SAN • SAN host interfaces • SAS • iSCSI • FC

3. Server A Server B Server C Ethernet JBOD A JBOD B JBOD C Server A Server B Server C Ethernet NAS Server A Server B Server C Ethernet SAN 3 categories of external storage • DAS • Direct-attached storage device • Generally attached / dedicated to a specific server • NAS • Network-attached storage • Connected to a server via a network • Can be shared or dedicated • SAN • Storage Area Network • Connected to server via a storage network • Can be shared or dedicated

4. Why use either a SAN or NAS? • Why consolidate anything? • Let’s consider an analogy • Greater efficiency • Simplified management • Increased utilization • Reduced cost • Leverage features

5. Server NAS Storage controller NFS/CIFS TCP/IP Disk(s) Data NIC HBA NAS detail • NAS • Provides file-level access to storage • Ethernet connectivity / TCP/IP • CIFS (Common Internet File System) • NFS (Network File System) • Networked file system allows for concurrent access to data • Several layers between data request and receipt

6. Server Storage controller Disk(s) Data HBA SAN detail • SAN • Provides block-level access to storage • Ethernet (iSCSI) • Fibre Channel • Concurrent access generally not allowed to specific datasets • Remote disk(s) appear as locally attached block devices to server

7. Interface Options • Serial attached SCSI (SAS) • iSCSI • Fibre Channel (FC)

8. SAS Basics and Benefits • SAS – Serial Attached SCSI • A serial communication protocol designed for transfer of SCSI commands and data to and from devices over point-to-point interconnections  • Key Benefits • New roadmap with industry-wide acceptance • Significant performance enhancements • 3-Gbps SAS x4 “wide” ports • Cost equivalent to parallel SCSI • Freedom from 15 drive maximum per SCSI channel

9. SAS Special Considerations • Distance limitations – 8 meters per discreet connection • Perceived complexity based on the newness of the technology • SAS expanders, which will support SAN-like capabilities for SAS, are still in development • Limited to the number of servers that can be attached – based on the number of SAS host ports on the storage system

10. SAS Positioning • Excellent solution for directly attaching one to three local servers to a single storage device • Cost-effectively facilitates one-room storage configurations • Offers outstanding performance • No networking expertise necessary – removes complexity • Low cost and simple to use • High bandwidth and low latency

11. iSCSI Basics and Benefits • iSCSI - internet Small Computer System Interface • A network protocol that enables transmission of SCSI commands and data over an IP-based network usually via an Ethernet interface • Key Benefits: • Low cost • Less complexity • Extensive knowledge base – expertise in every IT organization • Flexible configuration topologies • Extensive reach with no distance limitations • Future performance • 1Gb/s today with roadmap for 10Gb/s and beyond

12. iSCSI Special Considerations • Network congestion risks the dropping of frames – important to evaluate configuration to foresee any bottlenecks • Achievable performance is misunderstood • Hardware and connection parameters can be leveraged to achieve desired performance • Security at risk when sharing IP storage networks with the existing network • Separate storage traffic from normal LAN traffic • Disparate expertise and confusion over storage and networking IT roles

13. iSCSI Positioning • Interface of choice for entry-level and SMB storage networks where FC is cost prohibitive • iSCSI has turned the corner, with a large number of installations in companies of all sizes • Users are growing more familiar with the lower-cost alternative to FC • Reach – IP SANs can to be located virtually anywhere. • Minimal storage investment – utilize existing IP SAN and additional equipment is relatively inexpensive • Leverage existing IT resources – in-house IP expertise • Simplify installation and management – a mature technology with proven management tools can be easily facilitated • Extend shared storage benefits to all servers – with minimal per-server connectivity costs

14. FC Basics and Benefits • FC – Fibre Channel • A serial networking interface that supports the transmission of upper level protocols – including SCSI command sets and data – over fiber optic or copper cables • Key Benefits • Scalable – supports up to 16 million addresses. • Distance – 10,000 meters maximum cabling length • High bandwidth – low latency and high IOPs • Investment protection – auto-negotiating link speeds allowing for seamless integration into an existing 1Gb/s or 2 Gb/s environment • Congestion free with credit-based flow control delivering data as fast as the destination buffer is able to receive it.

15. FC Special Considerations • Steep learning curve for administrators unfamiliar with deployment and management • Expensive and complex • Costly FC SAN equipment and maintenance • Training personnel internally or hiring a service company is a significant addition to TCO • Low-cost servers will typically not be included as the investment to attach it can outweigh the cost of the server itself – does not always make financial sense to deploy

16. FC Positioning • Dominates SANs today and expected to retain dominance in the enterprise market • FC will maintain advantages in both performance and scalability • Most mature and time-proven designs • High addressability necessary for large customers with thousands of servers • Takes the fullest advantage of server clusters • 4, 8, 16 and up to 100 or more servers as needed • Data integrity – class of service settings guarantees delivery of frames

17. To simplify… Performance • Pick 2… FC SAS Scalability Cost iSCSI

18. Summary • DAS, NAS, and SAN have intrinsic differences • Cost • Performance • Ease of management • SAS, iSCSI, and FC • Cost vs. scalability vs. performance