Serial Attached SCSI SAS

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Serial Attached SCSI (SAS) SATA II Overview
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Why Should You Learn about SAS?

• SAS is a scalable, flexible, cost effective, high
  performance storage interface
• SAS adds new capabilities to SCSI
• If you have existing SCSI customers, they will be
  excited about SAS
• SAS brings new capabilities to SATA

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The Emergence of Serial Attached SCSI (SAS)

• Newest Storage Interface for Direct Attach
  Storage (DAS)
• SAS Is the Next Generation of SCSI
• Supported by the same ANSI T10 Standards
  Committee
• Successor to Ultra320 SCSI on Industry Roadmap
• Leverages SCSI Expertise
• Significant Performance Feature Set Enhancements

Source SCSI Trade Association Jan 2004
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SATA vs. Enterprise SATA Hard Drives
Compliments Of
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Enterprise Server Disk Drive Market Outlook

• Predict 70 of Disc sold for Enterprise Server
  will be SAS/SATA
• Success of SAS as new Direct Attach Storage
  replacement is well underway
• Analysts predict market will drive consolidation
  in PB1-PB6, capping FC growth.

Source IDC
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SAS is Compatible with SATA II!

• Feature SAS controllers can talk to SATA or SAS
  HD Drives
• SAS HDD - Used When Performance Reliability are
  Critical
• SATA HDD - Used When Capacity Cost Are Most
  Important
• SAS SATA HDD - Can be Mixed in Single System
• Benefit Server, Workstation, and External
  Enclosures Can be Standardized on SAS. This
  will
• Reduce Component Qualification Costs
• Reduce Enclosure SKUs and Inventories
• Provide cost parity with comparable SATA
  solutions

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Mechanical Interoperability
SAS HDD SATA HDD
Dual Ports
Single Ports
One Tiny Difference
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Learning Check
Top 5 OEMS
A primary advantage of SAS controllers is
A Their ability to communicate with SAS and
SATA HDDs B Their ability to communicate with
SAS and FC HDDs C Their ability to communicate
with SAS HDDs only D All of the above
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New Terms

• 1) SATA Architected, SATA Populated (SATA)
• A system that contains SATA Controllers and SATA
  HDDs
• Low cost, GREAT for certain markets (i.e.
  streaming, archive)
• 2) SAS Architected, SAS Populated (SAS)
• A system that contains SAS controllers, SAS HDD,
  and optionally SAS expanders
• X3 cost on HDD, top notch performance for IOP
  intensive applications
• 3) SAS Architected, SATA Populated (SAS/SATA)
• A system that contains SAS controllers, SATA HDD,
  and optionally SAS expanders
• This allows the creation of sophisticated
  topologies with low cost SATA HDD

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The Power of Serial Interfaces
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SAS - SCSI on Steroids! (Improvements Over SCSI)
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SAS SATA - The New Paradigm(SAS Increases the
Performance and Versatility of SATA based systems)
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HDD Connectivity Technology Comparison
SAS adds FC Capabilities
Significant Differences Exist
Fibre Channel
SAS
SATA II

Half-duplex
?
Performance
Full-duplex with Link Aggregation
Full Duplex

3.0 Gb/s
3.0 Gb/s Introduction 6.0 Gb/s in 2007
2.0 Gb/s 4 Gb/s in 2005
Connectivity
gt 6 m internal and external cables
1 m internal cable
15 m external cable (Copper)
?
Multipliers 15 HDD max

Expanders gt128 devices
?
127 devices FC-AL 16 Million Fabric

?
Availability
Dual-port HDDs
Single-port HDDs
Dual-port HDDs

?
Multi-initiator
Single-host
Multi-initiator

?
Driver Model
Software transparent with Parallel SCSI
Software transparent with Parallel ATA
Software transparent with Parallel SCSI
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Learning Check
True or False?
SAS hard drives (HDDs) will eventually displace
SATA hard drives in the marketplace?
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SATA-Only RAID SolutionsDirect Connect,
Backplane, and Multi-Lane
ONLY
X4 ML
Direct Connect via Backplane
Multi Lane
Direct Connect
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SAS/SATA RAID SolutionsIdentical to SATA PLUS
OR
X4 ML
Direct Connect via Backplane
Multi Lane
Direct Connect
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. . What SATA Does Not Have - SAS Expanders

• Expanders are a piece of silicon, most commonly
  found on a backplane into which HDDs plug
• Expanders allow 1 or more SAS controller ports to
  fan out to many HDDs
• Expanders supports SAS or SATA Disc Drives
• Mix and Match!!

4 Ports 12 HDDs!
OR
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SAS Expanders Wide Ports Are Key!!

• SAS Wide Ports are Unique in Storage
• No SCSI, SATA, or FC equivalent
• Nearest equivalent might be Ethernet Trunking
• Wide ports are used to aggregate bandwidth
• One or more SAS ports can be used to talk with
  many HDDs
• Definition A wide port is a single logical
  connection (i.e. port) between two devices built
  from 1-4 physical wires (i.e. links).
• Typical usage redundant connections between a
  HBA/RAID SAS controller and a SAS expander are
  configured as a wide port
• Wide ports are transparent to the host/OS and HDDs

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Expanders and Scalability The promise of SAS
OR
10 HDD 4 Ports!!
SAS Expanders brings the opportunity for the OEM
and System Builder to create a truly unique
product offering by scaling the number of SATA
drives way beyond typical applications..
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SAS RAID More Flexibility/Scalability than SATA
RAID
Direct Connect OR Multilane
X4 ML
X4 ML
X4 ML
X4 ML
16 Port SATA RAID 16 HDD
8 Port SAS RAID 40 HDD

• Flexibility for SATA and SAS Hard Drives
• Scalability using 8 Ports to 36 HDDs

• Limited Outside the Box Options
• Limited to 16 SATA Hard Drives

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Scalability Only SAS does this!!
OR
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Key Takeaways

• SAS adds new features to SCSI
• SAS brings new capabilities to SATA
• SAS provides
• Flexibility
• Scalability
• Cost-effective tiered storage solutions
• High performance for SAS and SATA systems

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The SAS Infrastructure
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