Cost Effective Network Storage Solutions

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Cost Effective Network Storage Solutions

• Paul von Stamwitz
• Storage Technology Strategist

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Agenda

• iSCSI overview
• iSCSI in a Direct-attached environment
• Building an iSCSI target with off-the-shelf
  hardware
• Topologies
• Considerations
• Performance
• Wrap-up

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iSCSI An Overview

• iSCSI is Internet SCSI (Small Computer System
  Interface), an Internet Protocol (IP)-based
  storage networking standard for linking data
  storage facilities.
• Developed by the Internet Engineering Task Force
  (IETF).
• By carrying SCSI commands over IP networks, iSCSI
  is used to facilitate data transfers over
  intranets and to manage storage over long
  distances.
• Because of the ubiquity of IP networks, iSCSI can
  be used to transmit data over local area networks
  (LANs), wide area networks (WANs), or the
  Internet and can enable location-independent data
  storage and retrieval.

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Storage Definitions

• Storage Area Networking (SAN)
• Connects heterogeneous servers to a managed pool
  of storage.
• Storage is accessed via blocks (SCSI)
• Scale storage and servers independently
• Uses a special purpose network (typically Fibre
  Channel.)
• Network Attached Storage (NAS)
• Connects heterogeneous servers to a shared
  repository.
• Acts like a traditional fileserver.
• Storage is accessed via files (NFS.)
• Uses the general purpose local area network
  (typically Ethernet.)
• Direct Attached Storage (DAS)
• Storage dedicated to a server.
• Storage is accessed via blocks (SCSI or ATA)
• Storage is usually located in the box or
  connected via an external cable (typically SCSI.)

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Where does iSCSI fit in?

• While iSCSI promises the ability to connect
  servers to block storage using general purpose
  networks over large distances, this is an
  evolving technology.
• You can also use iSCSI for Direct-Attached
  storage today.

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Why iSCSI for DAS? Heres what IDC says
Worldwide iSCSI Forecast and Analysis, 20032007

• DAS will grow 200 CAGR between 2003 and 2007
• DAS before SANs chronologically
• Combine iSCSI with maximum-capacity disk drives
  (Serial ATA), and integrated RAID processors for
  maximum market impact

iSCSI Analyzing the Future of IP Storage
Networks (IDC, 11/03)
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Why iSCSI for DAS? (contd)

• Server applications are requiring more and more
  storage.
• Capacity requirements are exceeding the confines
  of the box.
• Need to be able to scale storage behind the
  server.
• The server is iSCSI ready
• iSCSI initiator support built in the OS.
• Gbe ports on the motherboard or inexpensively
  added.
• Easy to use and easy to connect
• Point-to-point or simple switches
• Inexpensive
• The server is ready to connect.
• And you can build an iSCSI target using
  off-the-shelf hardware.

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Introducing the iTM iSCSI Target Module

• Standard Rack-mounted Disk Drive Enclosure
• 2U or 3U, 8 to 16 drives
• Standard Motherboard
• 1 or more embedded Gbe ports
• RAID controller
• SATA or SCSI drives
• OS (i.e. Linux)
• iSCSI target kernel

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iSCSI Target Module

• Appears to the server as a big drive
• Primarily used as expansion storage, managed by
  the server
• Headless Unit
• Remote configuration
• Boot from a IDE Flash Card
• Can be directly connected using a cross-over
  cable
• Connect multiple iTMs with a simple switch
• Use RAID 5
• For reliability similar to ECC for single
  drives
• For performance aggregate disk bandwidth
• Can aggregate iSCSI bandwidth with multiple Gbe
  links
• Can aggregate system bandwidth by RAIDing
  multiple iTMs

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iSCSI DAS Topologies

• Near-line Storage
• Expansion Storage behind a NAS header
• Disk-to-Disk Backup
• Video Surveillance
• High Performance Clusters
• Digital Content

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Example Direct Attach Security/Surveillance
Objective Offer a low cost iTM and add value
through router, switch and software appliances
2TB 3TB
POE
4 camera capacity is satisfied with an iSCSI
Target Module (iTM) populated with SATA disk
drives.
4 cameras requires 500GB of available capacity
each. Total 2TB Requirement
Security Server iSCSI Host (initiator)
Private switch Direct Attach Network
iSCSI Storage (Targets)
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Considerations

• Configuration
• iSCSI and RAID setup and maintenance should be
  integrated
• Should support remote upgrades
• Latencies
• Usually due to the TCP/IP overhead in server and
  target
• May want to consider a TOE
• SCSI vs. SATA drives
• SATA by far the most cost-effective
• Front-end interface is SCSI
• Conversion to SATA done in software or in the
  SATA RAID controller

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Considerations (contd)

• Command Queue Depth
• Rule of thumb 2 commands per spindle
• Redundancy
• Drive failover at the RAID controller
• iSCSI path failover with multiple Gbe links
• No controller failover
• Server can RAID multiple iTMs
• Multiple server access
• The iTM is on a private network (even though its
  Ethernet)
• Limited partitioning and LUN masking
• Can upgrade to SAN via an iSCSI Storage
  Provisioning Appliance or host-based storage
  virtualization software.

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Performance (IOMeter)
64K Sequential Writes
64K Sequential Reads
68 MB/s
77 MB/s
100
250
80
200
60
150
MB/s
MB/s
40
100
20
50
0
0
1
2
4
8
16
1
2
4
8
16
Queue Depth
Queue Depth
Local
iTM
Local
iTM
Redhat 8 for target O/S 8-drive SATA RAID 5
(3ware 8506)
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Wrap-up

• The market for iSCSI DAS is now
• Cost will be a major decision factor
• Combining iSCSI and SATA RAID is a win
• Linux solutions are available
• For both target and initiator
• Integrators can build iSCSI targets with the same
  hardware they use today for NAS

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Q A
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Backup Slides
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Using iTMs in a SAN environment
Multiple servers sharing provisioned storage,
managed by an in-band virtualization appliance.
iSCSI Host (initiators)
iSCSI Storage (Targets)
Provisioning Appliance
SATA RAID Ready