© 2009 EMC Corporation. All rights reserved. EMC Proven Professional The #1 Certification Program in the information storage and management industry Direct Attached Storage and Introduction to SCSI Chapter 5 Section 2 : Storage Networking Technologies and Virtualization

© 2009 EMC Corporation. All rights reserved. Chapter Objective Upon completion of this chapter, you will be able to: oDiscuss the benefits and challenges of DAS oDiscuss DAS management options oDiscuss evolution of SCSI oDescribe SCSI – 3 architecture oDiscuss SCSI addressing and communication model

© 2009 EMC Corporation. All rights reserved. Lesson: Direct Attached Storage Upon completion of this lesson, you will be able to: oDiscuss the benefits of DAS oDescribe the elements of DAS oDiscuss DAS management considerations oDiscuss DAS challenges

© 2009 EMC Corporation. All rights reserved. What is DAS? oUses block level protocol for data access Internal Direct Connect External Direct Connect

© 2009 EMC Corporation. All rights reserved. DAS Benefits oIdeal for local data provisioning oQuick deployment for small environments oSimple to deploy oLow capital expense oLow complexity

© 2009 EMC Corporation. All rights reserved. DAS Connectivity Options oATA (IDE) and SATA oPrimarily for internal bus oSCSI oParallel (primarily for internal bus) oSerial (external bus) oFC oHigh speed network technology oBuss and Tag oPrimarily for external mainframe oPrecursor to ESCON and FICON

© 2009 EMC Corporation. All rights reserved. DAS Management oInternal oHost provides: oDisk partitioning (Volume management) oFile system layout oDirect Attached Storage managed individually through the server and the OS oExternal oArray based management oLower TCO (Total Cost of Ownership) for managing data and storage Infrastructure

© 2009 EMC Corporation. All rights reserved. DAS Challenges oScalability is limited oNumber of connectivity ports to hosts oDifficulty to add more capacity oLimited bandwidth oDistance limitations oDowntime required for maintenance with internal DAS oLimited ability to share resources oArray front-end port oUnused resources cannot be easily re-allocated oResulting in islands of over and under utilized storage pools

© 2009 EMC Corporation. All rights reserved. Lesson Summary Key points covered in this lesson: oInternal and External DAS oDAS Benefit oDAS Management Options oDAS Limitations

© 2009 EMC Corporation. All rights reserved. Lesson: Introduction to SCSI Upon completion of this module, you will be able to: oDescribe SCSI-3 architecture oDiscuss SCSI device models with different port configurations oDescribe SCSI Addressing

© 2009 EMC Corporation. All rights reserved. Evolution of Parallel SCSI oDeveloped by Shugart Associates & named as SASI (Shugart Associates System Interface) oANSI acknowledged SCSI as an industry standard oSCSI versions oSCSI–1 oDefined cable length, signaling characteristics, commands & transfer modes oUsed 8-bit narrow bus with maximum data transfer rate of 5 MB/s oSCSI–2 oDefined Common Command Set (CCS) to address non-standard implementation of the original SCSI oImproved performance, reliability, and added additional features oSCSI–3 oLatest version of SCSI oComprised different but related standards, rather than one large document

© 2009 EMC Corporation. All rights reserved. SCSI–3 Architecture oSCSI command protocol oPrimary commands common to all devices oTransport layer protocol oStandard rules for device communication and information sharing oPhysical layer interconnect oInterface details such as electrical signaling methods and data transfer modes

© 2009 EMC Corporation. All rights reserved. oSCSI target device oExecutes commands issued by initiators oExamples: SCSI peripheral devices SCSI Device Model SCSI communication involves: oSCSI initiator device oIssues commands to SCSI target devices oExample: SCSI host adaptor

© 2009 EMC Corporation. All rights reserved. SCSI Device Model (Cont.) oDevice requests uses Command Descriptor Block (CDB) o8 bit structure oContain operation code, command specific parameter and control parameter oSCSI Ports oSCSI device may contain initiator port, target port, target/initiator port oBased on the port combination, a SCSI device can be classified as an initiator model, a target model, a target model with multiple ports or a combined model (target/initiator model). Example: oTarget/initiator device contain target/initiator port and can switch orientations depending on the role it plays while participating in an I/O operation oTo cater to service requests from multiple devices, a SCSI device may also have multiple ports (e.g. target model with multiple ports)

© 2009 EMC Corporation. All rights reserved. SCSI Addressing oInitiator ID - a number from 0 to 15 with the most common value being 7. oTarget ID - a number from 0 to 15 oLUN - a number that specifies a device addressable through a target. Initiator IDTarget ID LUN Target Initiator LUNs

© 2009 EMC Corporation. All rights reserved. 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

© 2009 EMC Corporation. All rights reserved. Lesson Summary Key points covered in this lesson: oSCSI – 3 Architecture oSCSI device model oSCSI addressing Additional Task Refer www,t10.org for updated information on SCSI

© 2009 EMC Corporation. All rights reserved. Chapter Summary Key points covered in this chapter: oDAS can be internal or external o DAS challenges oSCSI – 3 architecture oSCSI addressing

© 2009 EMC Corporation. All rights reserved. Check Your Knowledge oGive an example of when DAS is a good solution? oList SCSI Device Models with Different Port Configurations? oHow many devices SCSI can support? oWhich SCSI ID has highest priority? Additional Task Research on Serial Attached SCSI (SAS)

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