Investigating Serial Attached SCSI (SAS) over TCP (eSAS) and benchmarking eSAS prototype against legacy SAS UCCS Master’s Project Proposal Deepti Reddy 1

SCSI vs SAS SCSISAS TopologyParallel BusSerial Bus Speed3.2 Gbps3 Gbps, 6Gbps, 12Gbps Distance1 to 12 meters8 meters Number of Targets 14 devices128 expanders. > 16,000 with cascaded expanders DevicesSCSI onlySAS & SATA ConnectivitySingle PortDual Port Drive Form Factor 3.5”2.5” CostLowMedium 2

iSCSI & Related Work iSCSI protocol describes a means of transporting of the SCSI packets over TCP/IP  The iSCSI specification is revised and updated by the Internet Engineering task Force (IEFT).  Work by S. Aiken, D. Grunwald, A. Pleszkun and J. Willeke shows the performance of a commercial iSCSI software implementation compared quite favorably with fibrechannel [7]  Security in iSCSI based network storage systems can degrade the performance of the syste. Research by S. Chaitanya, K. Butler, A. Sivasubramaniam, P. McDaniel and M. Vilayannur looks at methods to improve iSCSI performance [10] 3

Typical SAS Topology - DISK DRIVES - EXPANDERS Driver ~8m 4

Motivation & Challenges  Overcome the distance and scalability limitations of traditional Serial Attached SCSI (SAS) by using eSAS.  Like iSCSI, eSAS takes advantage of existing internet infrastructure, internet management facilities as well as addresses distance limitations  Provide research results for future industry specification for eSAS and iSCSI. 5

eSAS Topology - DISK DRIVES - EXPANDERS MPT Driver - TCP link - SAS link Out of band SAS over TCP In-band SAS 6

eSAS Approach  The eSAS Request is initially sent by the eSAS Initiator to the eSAS Target over TCP.  The eSAS Target strips off the TCP header and sends the SAS frames using the SAS Initiator block on the eSAS Target to the SAS expander/drive.  The SAS expander/drive sends SAS frames to the eSAS Target.  Finally, the eSAS Target embeds the SAS frames received from the expander/drive over TCP and sends it to the eSAS Initiator. 7

eSAS Message Format  The above shows how a legacy SAS header and data are embedded in an ethernet frame.  iSCSI uses the same approach where the SCSI header and data are encapsulated in an Ethernet frame. Ethernet Header IP Header TCP Header eSAS Header eSAS Data Ethernet Trailer TCP Segment IP Datagram Ethernet Frame 8

eSAS Approach  The above diagram shows a typical eSAS (SSP Read ) Request & Response sequence diagram.  iSCSI uses a similar approach where the back-end between the iSCSI target and SCSI drives uses the legacy SCSI protocol. eSAS Request eSAS Initiator eSAS Target SAS Expander Open Address Frame Open Accept SAS Request Frame Data Frame. Data Frame eSAS Response Response Frame Data Frame. Data Frame 9

Goals of the project  Design and develop a prototype of eSAS system − Write a client program using C/C++ that sends a set of eSAS commands to a server. − Write a server program using C/C++ that receives a set of eSAS commands, processes them and responds to the client with eSAS responses.  Evaluate the eSAS solution and compare with legacy SAS. 10

Tasks and Timeline TaskTimelineStatus Research SAS protocol 1.5 monthsCompleted Understand iSCSI at a high-level 15 daysCompleted Investigate how to embed SAS traffic over TCP/IP 7 daysCompleted Research how to benchmark SAS 10 daysOngoing (Expected Completion – November 22 nd ) Proposal writing7 daysCompleted 11

Tasks and Timeline TaskTimelineStatus S/W development of the eSAS client mock up + S/W development of the eSAS server mock up using C/C++ ~1.5 monthsEstimated Completion – January 10th Final Project Report 15 daysEstimated Completion – January 28th Final Presentation + Defense 5 daysEstimated Completion – January 31 st 12

Deliverables 1.Research report on the design and implementation of the client and server application 2.Research report on the benchmarking results of eSAS prototype app vs legacy SAS. 3. The software client eSAS simulator developed for the project. 4. The software server eSAS simulator developed to test the client application 13

References [1] T10/1760-D Information Technology – Serial Attached SCSI – 2 (SAS-2), T10, 18 April 2009, Available from [2] Harry Mason, Serial attached SCSI Establishes its Position in the Enterprise, LSI Corporation, available from [3] J Satran, K Meth, C. Sapuntzakis, M. Chadalapka, E. Zeidner, RFC 3720 Internet Small Computer Systems Interface (iSCSI) Specification IETF, April 2004, available from [4] Cai, Y.; Fang, L.; Ratemo, R.; Liu, J.; Gross, K.; Kozma, M.; A test case for 3Gbps serial attached SCSI (SAS) Test Conference, Proceedings. ITC IEEE International, February 2006, available from [5] Heng Liao, Tim Symons, Rachelle Tant, Managing Access Control Through Zoning, PMC-Sierra Inc., Spetember 2005, available from 14

References [6] Kalmath Meth, Julian Satran, Design of the iSCSI Protocol, Mass Storage Systems and Technologies, (MSST 2003). Proceedings. 20th Mass Storage Systems and Technologies, (MSST 2003). Proceedings. 20th IEEE/11th NASA Goddard Conference onIEEE/11th NASA Goddard Conference on Mass Storage Systems and Technologies, April 2003, available from [7] Stephen Aiken, Dirk Grunwald, Andrew R. Pleszkun, Jesse Willeke, A Performance Analysis of the iSCSI Protocol 20 th IEEE/11 th NASA Goddard Conference on Mass Storage Systems and Technologies, 2003, available from [8] M. Rajagopal, E. Rodriguez, R. Weber, RFC 3821 Fibre Channel over TCP/IP (FCIP) standard, IETF, July 2004, available from [9] BLi Bigang, Shu Jiwu, Zheng Weimin, SCSI Target Simulator Based on FC and IP Protocols in TH-MSNS * Department of Computer Science and Technology, Tsinghua University, Beijing China,

References [10] S. Chaitanya, K. Butler, A. Sivasubramaniam, P. McDaniel, M. Vilayannur, Design, Implementation and Evaluation of Security in iSCSI-based Network Storage Systems, StorageSS '06 Proceedings of the second ACM workshop on Storage security and survivability, October 2006, available from 16