1. Storage Networking Technologies and Virtualization Section 2 DAS and Introduction to SCSI1

2. - 2 Section Objective Upon completion of this section, you will be able to: Describe the elements, connectivity, and management of: – Direct Attached Storage (DAS) – Network Attached Storage (NAS) – FC and IP Storage Area Networks (SAN) – Content Addressed Storage (CAS) and Discuss the benefits and challenges of each of the storage models Describe various virtualization technologies

3. Direct Attached Storage and Introduction to SCSI Chapter 5 DAS and Introduction to SCSI3

4. - 4 Chapter Objective Upon completion of this chapter, you will be able to: Discuss the benefits and challenges of DAS Discuss DAS management options Discuss evolution of SCSI Describe SCSI – 3 architecture Discuss SCSI addressing and communication model

5. DAS and Introduction to SCSI - 5 Lesson: Direct Attached Storage Upon completion of this lesson, you will be able to: Discuss the benefits of DAS Describe the elements of DAS Discuss DAS management considerations Discuss DAS challenges

6. DAS and Introduction to SCSI - 6 What is DAS?6 Uses block level protocol for data access Internal Direct Connect External Direct Connect

7. DAS and Introduction to SCSI - 7 DAS Benefits Ideal for local data provisioning Quick deployment for small environments Simple to deploy Reliability Low capital expense Low complexity

8. DAS and Introduction to SCSI - 8 DAS Connectivity Options ATA(133 MB/sec) (IDE) and SATA(150 MB/sec too 600) – Primarily for internal bus (40pin-disk to MB,34pin-drive to MB) (latest ATA Ultra DMA/133) SCSI – Parallel (primarily for internal bus) – Serial (external bus) FC – High speed network technology Buss and Tag – Primarily for external mainframe – Precursor to ESCON and FICON

9. DAS and Introduction to SCSI - 9 DAS Management Internal – Host provides: Disk partitioning (Volume management) File system layout – Direct Attached Storage managed individually through the server and the OS External – Array based management – Lower TCO for managing data and storage Infrastructure

10. DAS and Introduction to SCSI 10 DAS Challenges Scalability is limited – Number of connectivity ports to hosts – Number of addressable disks – Distance limitations Downtime required for maintenance with internal DAS Limited ability to share resources – Array front-end port, storage space – Resulting in islands of over and under utilized storage pools

11. DAS and Introduction to SCSI - 11 Lesson Summary Key points covered in this lesson: Internal and External DAS DAS Benefit DAS Management Options DAS Limitations

12. DAS and Introduction to SCSI - 12 Lesson: Introduction to SCSI Upon completion of this lesson, you will be able to: Describe SCSI-3 architecture Discuss SCSI device models with different port configurations Describe SCSI Addressing

13. DAS and Introduction to SCSI - 13 Evolution of Parallel SCSI Developed by Shugart Associates & named as SASI ANSI acknowledged SCSI as an industry standard SCSI versions – SCSI–1 Defined cable length, signaling characteristics, commands, & transfer modes Used 8-bit narrow bus with maximum data transfer rate of 5 MB/s – SCSI–2 Defined Common command Set (CCS) Improved performance, reliability, and added additional features – SCSI–3 Latest version of SCSI, Comprised different but related standards, rather than one large document.

14. DAS and Introduction to SCSI - 14 SCSI–3 Architecture SCSI command protocol – Primary commands common to all devices Transport layer protocol – Standard rules for device communication and information sharing Physical layer interconnect – Interface details such as electrical signaling methods and data transfer modes

15. DAS and Introduction to SCSI - 15 SCSI target device – Executes commands issued by initiators – Examples: SCSI peripheral devices Device requests contain Command Descriptor Block (CDB) SCSI Device Model SCSI communication involves: SCSI initiator device – Issues commands to SCSI target devices – Example: SCSI host adaptor

16. DAS and Introduction to SCSI - 16 SCSI Device Model (Cont.) CDB (command descriptor Block) structure – 8 bit structure – Contain operation code, command specific parameter and control parameter SCSI Ports – SCSI device may contain initiator port, target port, target/initiator port – Based on port combination device is classified – For example Target/initiator device contain target/initiator port and can switch orientations depending on the role it plays while participating in an I/O operation – To cater to service requests from multiple devices, a SCSI device may also have multiple ports

17. DAS and Introduction to SCSI - 17 SCSI Addressing Initiator ID - a number from 0 to 15 with the most common value being 7. Target ID - a number from 0 to 15 LUN - a number that specifies a device addressable through a target. Initiator IDTarget ID LUN Target Initiator LUNs

18. DAS and Introduction to SCSI - 18 SCSI Addressing Example Initiator IDTarget ID LUN c0c0 t0t0 d0d0 Port Host Storage Array Target (Front-end port) Target – t0 Initiator (HBA) Controller – c0 d0 d1 d2 Storage Volumes Host Addressing: Storage Volume 1 - c0t0d0 Storage Volume 2 - c0t0d1 Storage Volume 3 - c0t0d2 LUN

19. DAS and Introduction to SCSI19 CostOverall, IDE is a much cheaper solution. When compared with IDE, SCSI is often more expensive to implement and support. ExpansionIDE/EIDE allows 2 two devices per channel. Most computers have 2 channels. SCSI is capable of supporting up to 7 or 15 devices. EaseIDE is commonly a much easier product to setup than SCSI. Configuring SCSI can be more difficult for most users when compared to IDE. ATA/IDESCSI

20. ResourcesAll motherboards today have an ATA/IDE interface and unless additional drives are needed no additional resources need to be taken. Unlike IDE, SCSI requires an interface expansion card in most cases (unless the motherboard already has it). This means additional system resources will be required. DAS and Introduction to SCSI20 ATA/IDESCSI

21. DAS and Introduction to SCSI - 21 Lesson Summary Key points covered in this lesson: SCSI – 3 Architecture SCSI device model SCSI addressing Comparison of SCSI & IDE/ATA

22. DAS and Introduction to SCSI - 22 Chapter Summary Key points covered in this chapter: DAS can be internal or external Multiple hosts cannot share same storage ports DAS is made up of a CPU, connectivity, and storage devices DAS connectivity uses block-level access protocols SCSI – 3 architecture Parallel SCSI addressing SCSI Command model

23. DAS and Introduction to SCSI - 23 Check Your Knowledge What are the physical elements of DAS? Give an example of when DAS is a good solution. Describe internal DAS connectivity. Describe external DAS connectivity. List SCSI Device Models with Different Port Configurations. How many devices SCSI can support? Which SCSI ID has highest priority?