Storage Networking: Fibre, iSCSI, NAS

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Storage NetworkingFibre, iSCSI, NAS

• Graeme Holmes
• Cristie Data Products Ltd

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Agenda

• The Need For SAN
• Fibre, iSCSI and NAS

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The Need for SAN
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Current Situation

• Direct Attached Storage
• Locally attached disk
• SCSI protocol

• Islands of Storage
• Available storage on server B cannot be
  utilised by server A
• Limited scalability
• High Management Costs
• Inflexible

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DAS - Scalability

• Limited to the servers predetermined capacity
• External expansion with SCSI is limited to 15
  devices per channel
• 12M Distance limitation
• Expensive to scale
• High management costs
• Still has over/under utilisation issues

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Centralised storage - NAS

• Network Attached Storage
• Consolidate File Servers
• No need to buy servers to add capacity
• File level storage only
• Databases require block-level storage
• Storage traffic moves onto LAN
• Limited scalability
• Management

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Centralised Storage - SAN

• Dedicated Storage Network
• Centralised storage management
• Block level storage
• File applications
• Storage traffic off the LAN
• Flexible and scalable
• Any server can have access to any available
  storage
• Increased Data Availability

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SAN Benefits

• Grows storage independently of servers
• Centralised high-availability storage reduces
  storage management overhead
• Scalable - Supports thousands of interconnected
  devices
• High aggregate bandwidth, multiple paths
• 1Gb 2Gb fibre, Gigabit Ethernet
• Application clustering possible on wider scale

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SAN - Disaster Recovery

• To assure continued operations, data can be
  mirrored within the
• same subsystem
• to adjacent subsystem
• to a subsystem in a remote location

• Storage mirrored or replicated
• Block level transfer

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Fibre, iSCSI and NAS
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Fibre Topologies

• Point-to-point
• Only two FC devices connected directly together
• No sharing of media - devices each benefit from
  total link bandwidth

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Fibre Topologies

• Arbitrated Loop
• 127 addresses or 126 devices per loop
• Bandwidth shared between devices.
• Blocking, shared media
• 100MB/sec speed.
• Lowest cost Fibre protocol

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Fibre Topologies

• Switched Fabric
• Connect millions of devices
• All devices can communicate at the same time
  media is not shared.
• 100 or 200MB/sec between nodes

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Other Protocols

• FC-IP Fibre channel frames over IP
• iFCP mapping FCP (serial SCSI over Fibre
  Channel) into and out of IP

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Fibre SAN Management
Management of the network, storage devices
storage software can be performed from any
authorised host on the network
Zones prevent devices external to a given zone
from communicating within that zone. This can
be achieved by Port Zoning at the switch level or
LUN masking within the storage array.
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Benefits of Fibre SAN

• Massively scaleable
• High Performance
• I/O intensive applications
• Backup
• Centralises management of storage
• Secure

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Disadvantages

• High hardware and software costs
• High implementation costs
• New skills required
• Distance limitation for Disaster Recovery

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iSCSI - What is it?

• Encapsulates block-level SCSI commands in a
  TCP/IP frame
• A method of creating Storage Networks over IP
• iSCSI storage NIC connects storage resources over
  Ethernet
• Two key components
• Initiator an iSCSI driver embedded in the server
  
• Target a gateway device that routes data between
  server storage

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iSCSI
User
IP Network
IP packet
IP packet
iSCSI Initiator Adapter
iSCSI Target Adapter
Storage Device
Server
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TCP Off-load Engines

• iSCSI on standard NICs
• Uses CPU for TCP iSCSI processing
• Software iSCSI with TCP offload
• TCP processing by TOE card
• Hardware iSCSI
• TCP iSCSI processing by TOE card

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Off-load Engines
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iSCSI Benefits

• Leverages existing investment in technology and
  skills
• Relatively low implementation costs
• Similar speeds to fibre channel
• 10 Gig Ethernet, 40 Gig?
• No distance limitations

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Disadvantages

• Perceived as less secure than fibre channel
• Relatively new standard

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NAS

• File-based storage architecture
• Resources attach directly to LAN
• File Server, Home Directories, image storage etc
• File level storage only
• Databases require block-level storage
• NAS Headers
• NAS device which uses portion of SAN storage

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NAS Advantage

• Familiar technology
• Minimal training
• Relatively low-cost way of adding disk space
• Provides some flexibility
• Additional units can be easily added

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Storage Virtualisation

• Pooling of disparate systems into single
  consolidated view a storage pool
• Removes LUN limitation and resizing issues
• Also enables snapshotting, replication etc
• In band Feature rich
• Out of band Out of data path

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Summary

• Fibre SAN
• Best performance security
• High cost, new skills
• iSCSI SAN
• Simpler implementation
• leverage existing investment in technology and
  skills
• Virtualisation
• Lower storage TCO
• Improve data availability
• NAS Mixed NAS/SAN environments

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Thank you