Transcript Investigating Serial Attached SCSI (SAS) over TCP (eSAS

Investigating Serial Attached
SCSI (SAS) over TCP (eSAS)
and benchmarking eSAS
prototype against legacy SAS
UCCS
Master’s Project Proposal
Deepti Reddy
1
Typical SAS Topology
MPT
Driver
~8m
- DISK DRIVES
- EXPANDERS
2
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.
3
eSAS Topology
Out of band SAS
over TCP
MPT
Driver
In-band SAS
- DISK DRIVES
- TCP link
- EXPANDERS
- SAS link
4
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.
5
eSAS Approach
Ethernet
Header
IP
Header
TCP
Header
eSAS
Header
eSAS
Data
Ethernet
Trailer
TCP Segment
IP Datagram
Ethernet Frame
 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
6
data are encapsulated in an Ethernet frame.
eSAS Approach
SAS
Expander
eSAS
Target
eSAS
Initiator
eSAS
Request
Open Address
Frame
Open Accept
SAS Request
Frame
Data Frame
Data Frame
.
.
Data Frame
.
.
Data Frame
Response
Frame
eSAS
Response

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
7
SCSI protocol.
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.
8
Tasks and Timeline
Task
Timeline
Status
Research SAS
protocol
1.5 months
Completed
Understand iSCSI
at a high-level
15 days
Completed
Investigate how to
embed SAS traffic
over TCP/IP
7 days
Completed
Research how to
benchmark SAS
10 days
Ongoing (Expected
Completion –
November 22nd)
Proposal writing
7 days
Completed
9
Tasks and Timeline
Task
Timeline
Status
S/W development ~1.5 months
of the eSAS client
mock up + S/W
development of the
eSAS server mock
up using C/C++
Estimated
Completion –
January 10th
Final Project
Report
15 days
Estimated
Completion –
January 28th
Final Presentation
+ Defense
5 days
Estimated
Completion –
January 31st
10
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
11
References
[1] T10/1760-D Information Technology – Serial Attached SCSI – 2 (SAS-2),
T10, 18 April 2009,
Available from http://www.t10.org/drafts.htm#SCSI3_SAS
[2] Harry Mason,
Serial attached SCSI Establishes its Position in the Enterprise,
LSI Corporation,
available from http://www.scsita.org/aboutscsi/sas/6GbpsSAS.pdf
[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 http://www.ietf.org/rfc/rfc3720.txt
[4] Cai, Y.; Fang, L.; Ratemo, R.; Liu, J.; Gross, K.; Kozma, M.;
A test case for 3Gbps serial attached SCSI (SAS)
Test Conference, 2005. Proceedings. ITC 2005. IEEE International, February
2006,
available from http://ieeexplore.ieee.org/xpls/abs_all.jsp?arnumber=1584027
[5] Heng Liao, Tim Symons, Rachelle Tant,
Managing Access Control Through Zoning,
PMC-Sierra Inc., Spetember 2005,
available from
http://www.scsita.org/aboutscsi/sas/WP_PMC_Sierra_SAS_0905.pdf
12
References
[6] Kalmath Meth, Julian Satran,
Design of the iSCSI Protocol,
Mass Storage Systems and Technologies, 2003. (MSST 2003). Proceedings. 20th
IEEE/11th NASA Goddard Conference on Mass Storage Systems and Technologies,
April 2003,
available from
http://ieeexplore.ieee.org/xpls/abs_all.jsp?arnumber=1194848&tag=1
[7] Stephen Aiken, Dirk Grunwald, Andrew R. Pleszkun, Jesse Willeke,
A Performance Analysis of the iSCSI Protocol
20th IEEE/11th NASA Goddard Conference on Mass Storage Systems and
Technologies, 2003,
available from
http://www.storageconference.org/2003/papers/20-Aikens-Performance.pdf
[8] M. Rajagopal, E. Rodriguez, R. Weber,
RFC 3821 Fibre Channel over TCP/IP (FCIP) standard,
IETF, July 2004,
available from http://tools.ietf.org/html/rfc3821
[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, 2005
13