1. Lecture 17: Storage Systems
COSC6376 Cloud Computing
Lecture 17: Storage Systems
Instructor: Weidong Shi (Larry), PhD
Computer Science Department
University of Houston

2. Storage Area Network and Storage Virtualization

3. Introduction To Storage: Overview of the storage subsystem
Storage types
Single Disk Drive
Storage Array
SCSI device
DAS
NAS
SAN
iSCSI
Introduction To Storage: Overview of the storage subsystem

4. Direct attached storage (internal)
Computer System
CPU
Memory
Bus
I/O - RAID
Controller
Disk Drives
Introduction To Storage: Overview of the storage subsystem

5. Direct attached storage (internal)
12345
John Smith
1424 Main Street
Computer System
CPU
Memory
Bus
I/O - RAID
Controller
Disk Drives
Data
Introduction To Storage: Overview of the storage subsystem

6. Direct attached storage (internal)
12345
John Smith
1424 Main Street
Computer System
CPU
Memory
Bus
I/O - RAID
Controller
Disk Drives
Introduction To Storage: Overview of the storage subsystem

7. DAS w/internal controller and external storage
12345
John Smith
1424 Main Street
CPU
Memory
Bus
I/O - RAID
Controller
Computer System
Disk Drives
Disk Enclosure
Introduction To Storage: Overview of the storage subsystem

8. Attach large number of disks
9/18/ :34 PM
Attach large number of disks
4-Processor AMD Dual Core Opteron can handle 2.5 GB/s or more sequential read and write data traffic
Each controller connects 8 point-to-point SATA Drives – Average 400 MB/s/card
PCI-X SATA Controller
400 GB
PCI-X SATA Controller
400 GB
16 TB Raw
Disk Space
12 TB
RAID 5
8 TB
Mirrored
PCI-X SATA Controller
400 GB
400 GB
PCI-X SATA Controller
400 GB
PCI-X SATA Controller
© 2005 Microsoft Corporation. All rights reserved.
This presentation is for informational purposes only. Microsoft makes no warranties, express or implied, in this summary.

9. Backblaze

10. Backblaze Storage Pods: 67 terabyte 4U servers

11. Comparing internal and external storage
RAID controllers and disk drives are internal to the server
SCSI, ATA, or SATA protocol between controller and disks
Server
Storage
Server
Disk Drives
RAID Controller
RAID Controller
RAID controller is internal
SCSI or SATA protocol between controller and disks
Disk drives are external
Storage
Internal Storage
Disk Drives
SCSI Bus w/ external storage
Introduction To Storage: Overview of the storage subsystem

12. Direct attached storage
Direct Attached Storage (DAS)
Storage is captive ‘behind’ the server
Server CPU must handle user I/O requests, but also:
User-database inquiries
User file/print serving
Data-integrity checking
Communication with other devices
Data access is file system and platform dependent
Costly to scale; complex to manage
Clients
IP Network
Servers
Win
Linux
Win
Linux
Unix FC FC
SCSI
Direct-Attached Storage (DAS)

13. DAS w/external controller and external storage
Storage System
12345
John Smith
1424 Main Street
Computer System
CPU
Memory
Bus
HBA
Disk Drives
Disk Enclosure
RAID Controller
Introduction To Storage: Overview of the storage subsystem

14. Introduction To Storage: Overview of the storage subsystem
DAS over Fibre channel
Server
HBA
HBA is internal
Fibre Channel protocol between HBAs and external RAID controller
Storage
Disk Drives
Disk drives and
RAID controller are external
RAID Controller
External SAN Array
Introduction To Storage: Overview of the storage subsystem

15. Introduction To Storage: Overview of the storage subsystem
I/O Transfer
RAID Controller
Contains the “smarts”
Determines how the data will be written (striping, mirroring, RAID 10, RAID 5, etc.)
Host Bus Adapter (HBA)
Simply transfers the data to the RAID controller.
Doesn’t do any RAID or striping calculations.
“Dumb” for speed.
Required for external storage.
Introduction To Storage: Overview of the storage subsystem

16. SCSI Small Computer System Interface
9/18/ :34 PM
SCSI Small Computer System Interface
© 2006 Microsoft Corporation. All rights reserved. Microsoft, Windows, Windows Vista and other product names are or may be registered trademarks and/or trademarks in the U.S. and/or other countries.
The information herein is for informational purposes only and represents the current view of Microsoft Corporation as of the date of this presentation. Because Microsoft must respond to changing market conditions, it should not be interpreted to be a commitment on the part of Microsoft, and Microsoft cannot guarantee the accuracy of any information provided after the date of this presentation. MICROSOFT MAKES NO WARRANTIES, EXPRESS, IMPLIED OR STATUTORY, AS TO THE INFORMATION IN THIS PRESENTATION.

17. Terminology Initiator: A SCSI device that requests an operation to be
performed by another SCSI device.
Host Adapter: A Controller Board that translates host I/O requests
into SCSI requests.
Target: A SCSI device that performs an operation as requested
by an initiator.
Logical Unit: A Physical or Virtual device addressable through a
target.
LUN: Logical Unit Number. An encoded three-bit identifier
for the logical unit.

18. single initiator, single target
SCSI configuration
single initiator, single target
LUN0
Initiator
Target
LUN1
SCSI Bus
LUN2

19. Single initiator, multiple targets
SCSI configuration
Single initiator, multiple targets T
Target 0
Initiator 7
Target 1
SCSI Bus
Target n T
SCSI Bus Terminator

20. Multiple initiators, multiple targets
SCSI configuration
Multiple initiators, multiple targets T
Target 0
Initiator 7
Target 1
SCSI Bus
Initiator 6
Target n T

21. The SCSI I/O Channel
SCSI is the dominant protocol used to communicate between servers and storage devices in open system
SCSI I/O channel is a half-duplex pipe for SCSI CDBs and data
Parallel bus evolution
Bus width: 8, 16 bits
Bus speed: 5–80 Mhz
Throughput: 5–320 MBps
Devices/bus: 2–16 devices
Cable length: 1.5m–25m
A network approach can scale the I/O channel in many areas (length, devices, speed)
Applications
Raw
File System
Block Device
SCSI Generic
TCP/IP Stack
NIC Driver
Adapter Driver
Ethernet NIC
SCSI Adapter
Half-Duplex
SCSI
I/O Channel
SCSI
SCSI Initiator
Ethernet
SCSI CDB: SCSI Command Descriptor Block Used to Relay SCSI Commands, Parameters, and Status between SCSI Initiators and SCSI Targets; Typically 6, 10, or 12 Byte Block
SCSI Target
IP Storage Networking FCIP/iSCSI. Steve Tegeler

22. Networking the I/O Channel
Same SCSI protocol (SCSI-3) carried over a network transport layer via serial implementation
Transport must not jeopardize SCSI payload (security, integrity, latency)
Two primary transports to choose from today: Fibre Channel and IP
A networked I/O channel allows for multiple improvements:
Distance limitations greatly increased
High number of addressable devices
Host System
SCSI
Initiator
Channel
Controller
Networked
I/O Channel
Network
Target and LUNs
IP Storage Networking FCIP/iSCSI. Steve Tegeler

23. Fibre channel networking
Very common method for networking SCSI
Fibre Channel provides high-speed transport for SCSI payload
Fibre Channel SAN overcomes many shortcomings of DAS including:
Addressing for up to 16-million nodes (24 bits)
Loop (shared) and Fabric (switched) transport
Speeds of 100 or 200 MBps (1 or 2 Gbps)
Distance of up to 10km (without extenders)
Support for multiple protocols
Combines best attributes of a channel and a network
Host System
SCSI
Initiator
Fibre Channel HBA
Fibre Channel Fabric
Target
IP Storage Networking FCIP/iSCSI. Steve Tegeler

24. IP: an alternate I/O transport
Host System
Viable transport for I/O traffic
Similar characteristics to Fibre Channel:
Addressing for close to 4 billion nodes (IPv4)
Primarily a switched transport (with routing)
Ethernet speeds of 1/10 Gbps or various WAN speeds
Support for multiple high-level protocols
Cost and manageability advantages with IP
IP knowledge base widespread in industry
SCSI
Initiator
IP “Channel Adapter”
IP Network
Target
IP Storage Networking FCIP/iSCSI. Steve Tegeler

25. 9/18/ :34 PM
Fibre Channel
© 2006 Microsoft Corporation. All rights reserved. Microsoft, Windows, Windows Vista and other product names are or may be registered trademarks and/or trademarks in the U.S. and/or other countries.
The information herein is for informational purposes only and represents the current view of Microsoft Corporation as of the date of this presentation. Because Microsoft must respond to changing market conditions, it should not be interpreted to be a commitment on the part of Microsoft, and Microsoft cannot guarantee the accuracy of any information provided after the date of this presentation. MICROSOFT MAKES NO WARRANTIES, EXPRESS, IMPLIED OR STATUTORY, AS TO THE INFORMATION IN THIS PRESENTATION.

26. Fibre channel: what is it?
Fibre Channel is a network protocol implemented specifically for dedicated storage networks
Fibre Channel utilizes specialized
Switches
Host Bus Adapters
RAID controllers
Cables
Introduction To Storage: Overview of the storage subsystem

27. Fibre channel components
Server A
Server B
Server C
HBA
HBA
HBA
HBA
HBA
HBA
switch
switch
Servers
Host Bus Adapters
Cables
Fiber optic or copper
Fibre Channel Switches
Two switches for redundancy
Fibre Channel Storage Array
Two RAID Controllers for redundancy
4–100+ disk drives per array
A true storage network
Multiple servers
Multiple switches
Multiple Storage Arrays
Disk Drives
RAID Controller
RAID Controller
FC Storage Array
Introduction To Storage: Overview of the storage subsystem

28. What is fibre channel?
A high-speed transmission technology used as a peripheral channel or network backbone.
FC1: Over 1G bits per second
FC2: Over 2G bits per second
It supports several common transport protocols like Internet Protocol (IP) and SCSI.
It operates over copper and fiber optic cables at distances of up to 10 Kilometers.
Up to 127 devices (SCSI: 15)
Up to 10 km of cabling (3-15 ft. for SCSI)
Physical interconnect can be copper or fiber optic
It is supported by many suppliers.

29. Fibre channel – (continued)
How does it work?
Serial interface
Data is transferred across a single piece of medium at the fastest speed supported
No complex signaling required
Hot-pluggable
Devices can be removed or added at will with no ill effects to data communications
Provides a data link layer above the physical interconnect, analogous to Ethernet
Sophisticated error detection at the frame level
Data is checked and resent if necessary
Introduction To Storage: Overview of the storage subsystem

30. Current standards:
Performance from 266 megabits/second to over 4 gigabits/second
High-bandwidth utilization with distance insensitivity.
Support for multiple cost/performance levels, from small systems to super computers
Ability to carry multiple existing interface command sets, including Internet Protocol (IP), SCSI, and audio and video

31. Fibre channel – frame dissection
Up to 2048 byte payload
4 byte checksum for each frame
Introduction To Storage: Overview of the storage subsystem

32. Introduction To Storage: Overview of the storage subsystem
Fibre channel
What’s with the funny name?
Some background history required
Originally developed to only support fiber optic cabling
When copper cabling support was added, ISO decided not to rename the technology
ISO changed to the French spelling to reduce association with fiber optics only medium
Introduction To Storage: Overview of the storage subsystem

33. Fibre channel interface layers
RAID Controller
Disk Drive
Fibre Channel
Device Driver
SCSI Protocol
Fibre Channel
Fiber Optic or Copper Cabling
Introduction To Storage: Overview of the storage subsystem

34. Introduction To Storage: Overview of the storage subsystem
SCSI vs. Fibre Channel
Used with SAN
Lots of built-in redundancy with connections
Redundant network
HBA is fibre channel hardware
Standards:
FC1: 100 MB/sec
FC2: 200 MB/sec
Provides a data link layer above the physical interconnect
Analogous to Ethernet
FC is a network of devices
It can be media independent- copper or fibre optic
Fibre Channel limitations:
Cable length: Up to 10 kilometers (more a limitation of cable than FC itself)
Up to 127 devices
# of disk drives
Interface for internal storage to external disks
Potential down time w/ SCSI
Single bus
RAID controller is SCSI hardware
Standards:
Ultra2 (80 MB/sec)
Ultra 160 (160 MB/sec)
Ultra 320 (320 MB/sec)
Media specific (copper only)
SCSI Limitations:
Cables can’t be any longer than 3 feet for single ended; 15 feet for LVD (low voltage differential)
No more than 15 devices on a SCSI bus
# of disk drives
Introduction To Storage: Overview of the storage subsystem

35. 9/18/ :34 PM
iSCSI
© 2006 Microsoft Corporation. All rights reserved. Microsoft, Windows, Windows Vista and other product names are or may be registered trademarks and/or trademarks in the U.S. and/or other countries.
The information herein is for informational purposes only and represents the current view of Microsoft Corporation as of the date of this presentation. Because Microsoft must respond to changing market conditions, it should not be interpreted to be a commitment on the part of Microsoft, and Microsoft cannot guarantee the accuracy of any information provided after the date of this presentation. MICROSOFT MAKES NO WARRANTIES, EXPRESS, IMPLIED OR STATUTORY, AS TO THE INFORMATION IN THIS PRESENTATION.

36. Introduction To Storage: Overview of the storage subsystem
iSCSI: what is it?
An alternate form of networked storage
Utilizes a TCP/IP network
Encapsulates native SCSI commands in TCP/IP packets
Supported in Windows Server and Linux
TCP/IP Offload Engines (TOEs) on NICs speed up packet encapsulation
Introduction To Storage: Overview of the storage subsystem

37. Public or Private Ethernet network
iSCSI storage
Public or Private Ethernet network
iSCSI Storage
NIC or iSCSI HBA
Server
NIC or iSCSI HBA
SCSI commands are encapsulated in TCP/IP packets
Disk Drives
Server has a Network Interface Card or iSCSI HBA
iSCSI HBAs use TCP/IP Offload Engine (TOE)
RAID Controller
Introduction To Storage: Overview of the storage subsystem

38. IP storage networking
IP storage networking provides solution to carry storage traffic within IP
Uses TCP: a reliable transport for delivery
Applicable to local data center and long-haul applications
Two primary protocols:
iSCSI—Internet-SCSI—used to transport SCSI CDBs and data within TCP/IP connections
FCIP—Fibre-Channel-over-IP—used to transport Fibre Channel frames within TCP/IP connections—any FC frame—not just SCSI IP
TCP
iSCSI
SCSI
Data IP
TCP
FCIP FC
SCSI
Data
IP Storage Networking FCIP/iSCSI. Steve Tegeler

39. SCSI architectural model transports
SCSI Block Commands
SCSI Stream
Commands
Parallel SCSI Transport
SCSI Applications (File Systems, Databases)
Parallel SCSI
Interfaces
SCSI Device-Type Commands
SCSI Generic Commands
SCSI Transport Protocols
Layer 3 Network Transport
Layer 2 Network
Fibre Channel
Ethernet, PPP, HDLC…
Other SCSI Commands IP
TCP
SCSI Commands, Data, and Status
FCP SCSI over FC
iSCSI SCSI over TCP/IP
IP Storage Networking FCIP/iSCSI. Steve Tegeler

40. iSCSI for storage consolidation
IP access to open systems iSCSI and Fibre Channel storage
iSCSI driver is loaded onto hosts on Ethernet network
Able to consolidate servers via iSCSI onto existing storage arrays
Able to build Ethernet-based SANs using iSCSI arrays
iSCSI
iSCSI-Enabled
Hosts (Initiators)
iSCSI
iSCSI
iSCSI
iSCSI Array (Target)
IP Network
iSCSI Gateway
FC Fabric
FC HBA-Attached Host (Initiator)
Storage Pool (Target)
IP Storage Networking FCIP/iSCSI. Steve Tegeler

41. iSCSI for remote block access
Block access to remote storage over IP
Application must tolerate latency for long distances
Metro Ethernet services offer lower-latency transport alternative
Remote backup over IP WAN
Centralized management from centralized storage
iSCSI
iSCSI-Enabled
Host
Site A
IP WAN
Site B
iSCSI Device
Remote
Mirrors
FC Fabric
Storage Pool
IP Storage Networking FCIP/iSCSI. Steve Tegeler

42. iSCSI architecture: software driver
Host
Applications
File System
iSCSI GW Device
iSCSI Host Driver
Block Device
iSCSI GW Module
SCSI Generic
SCSI Driver
TCP/IP Driver
iSCSI
TCP/IP Stack
FC HBA
GigE NIC
NIC Driver
Adapter Driver
IP Network
NIC
SCSI Adapter
Fibre Channel
iSCSI Path
Conventional SCSI Path
IP Storage Networking FCIP/iSCSI. Steve Tegeler

43. OS support OS vendors support native iSCSI drivers Applications
iSCSI Software Driver
File System
Block Device
SCSI Generic
iSCSI
TCP/IP Stack
Adapter Driver
NIC Driver
NIC Adapter
SCSI Adapter
IP Storage Networking FCIP/iSCSI. Steve Tegeler

44. iSCSI HBAs and TCP offload engines (TOEs)
Offloads TCP and, optionally, iSCSI processing into hardware
Relieves host CPU from:
TCP processing—16-bit checksum per packet
iSCSI—optional 32-bit header and data digests (CRC32C)
Applications
File System
Block Device
SCSI Generic
TCP/IP Stack
NIC Driver
iSCSI Driver
TOE Driver
HBA Driver
Adapter Driver
TCP/IP Stack
TCP/IP Stack
iSCSI
SCSI Adapter
TCP Offload
iSCSI and TCP Offload
IP Storage Networking FCIP/iSCSI. Steve Tegeler

45. Introduction To Storage: Overview of the storage subsystem
Fibre channel vs. iSCSI
Fibre Channel
The current market leader for shared storage technologies
Provides the highest performance levels
Designed for mission-critical applications
Cost of components is relatively high, particularly per server HBA costs
Relatively difficult to implement and manage
iSCSI
Performance can approach Fibre Channel speeds
A better fit for databases than NAS
A good fit for Small to Medium Size Businesses
Relatively inexpensive, compared to Fibre Channel
Relatively easy to implement and manage .
Introduction To Storage: Overview of the storage subsystem

46. Example performance impact on CPU utility %
FC vs. iSCSI TOE vs. iSCSI SW Driver
iSCSI SW Driver
iSCSI TOE
FC HBA
CPU %
Throughput MB/s

47. 9/18/ :34 PM
SAN
© 2006 Microsoft Corporation. All rights reserved. Microsoft, Windows, Windows Vista and other product names are or may be registered trademarks and/or trademarks in the U.S. and/or other countries.
The information herein is for informational purposes only and represents the current view of Microsoft Corporation as of the date of this presentation. Because Microsoft must respond to changing market conditions, it should not be interpreted to be a commitment on the part of Microsoft, and Microsoft cannot guarantee the accuracy of any information provided after the date of this presentation. MICROSOFT MAKES NO WARRANTIES, EXPRESS, IMPLIED OR STATUTORY, AS TO THE INFORMATION IN THIS PRESENTATION.

48. Introduction To Storage: Overview of the storage subsystem
SAN: what is it?
Storage Area Network
A network whose primary purpose is the transfer of data between storage systems and computer systems
Fibre Channel is the primary technology utilized for SANs
Can be implemented with dedicated iSCSI networks
Introduction To Storage: Overview of the storage subsystem

49. Benefits of SAN/consolidated storage
Reduce cost of external storage
Increase performance
Centralized and improved tape backup
LAN-less backup
High-speed
Consolidation with > 70TB of storage
Introduction To Storage: Overview of the storage subsystem

50. Introduction To Storage: Overview of the storage subsystem
NAS: what is it?
Network Attached Storage
Utilizes a TCP/IP network to “share” data
Uses file sharing protocols like Unix NFS
Storage “Appliances” utilize a stripped-down OS that optimizes file protocol performance
Introduction To Storage: Overview of the storage subsystem

51. Networked attached storage
Public or Private Ethernet network
NAS Server
NIC
Server
NIC
All data converted to file protocol for transmission (may slow down database transactions)
Storage
Disk Drives
Server has a Network Interface Card
No RAID Controller or HBA in the server
RAID Controller
Introduction To Storage: Overview of the storage subsystem

52. NAS vs. SAN NAS SAN Access Methods File access Disk block access
Access Medium
Ethernet
Fiber Channel
Architecture
Decentralized
Centralized
Transport Protocol
Layer over TCP/IP
SCSI/FC and SCSI/IP
Efficiency
Less
More
Sharing and Access Control
Good
Poor
Typical Applications
Web
Database
Typical Clients
Workstations
Database servers

53. Storage Virtualization
9/18/ :34 PM
Storage Virtualization
© 2006 Microsoft Corporation. All rights reserved. Microsoft, Windows, Windows Vista and other product names are or may be registered trademarks and/or trademarks in the U.S. and/or other countries.
The information herein is for informational purposes only and represents the current view of Microsoft Corporation as of the date of this presentation. Because Microsoft must respond to changing market conditions, it should not be interpreted to be a commitment on the part of Microsoft, and Microsoft cannot guarantee the accuracy of any information provided after the date of this presentation. MICROSOFT MAKES NO WARRANTIES, EXPRESS, IMPLIED OR STATUTORY, AS TO THE INFORMATION IN THIS PRESENTATION.

54. What and where can storage Potential Areas of Virtualization
be virtualized?
SNIA Storage Model
Storage Networking Industry Association
Potential Areas of Virtualization
Storage Virtualization aims to provide a layer of abstraction to manage storage and reduce complexity !!! 3
File Level Virtualization 2
Host Level Virtualization * 6
Network Virtualization
Block Virtualization 4
* * 5
Device Virtualization 1
Storage Level Virtualization
Source: The Storage Networking Tutorials, SNIAVIRT- Page 20
* Host aka Server
** Device=aggregation of Host and Network (Meta Data)

55. SNIA storage virtualization taxonomy
Copyright © 2009 EMC Corporation. Do not Copy - All Rights Reserved.
SNIA storage virtualization taxonomy
Storage
Virtualization
Block
Disk
File System,
File/record
Other Device
Tape, Tape Drive,
Tape Library
Network
Based Virtualization
Storage Device/Storage
Subsystem Virtualization
Host Based
In-band
Out-of-band
What is created
Where it is done
How it is implemented
The SNIA (Storage Networking Industry Association) storage virtualization taxonomy provides a systematic classification of storage virtualization, with three levels defining what, where, and how storage can be virtualized. The first level of the storage virtualization taxonomy addresses “what” is created. It specifies the types of virtualization: block virtualization, file virtualization, disk virtualization, tape virtualization, or any other device virtualization. Block-level and file-level virtualization are the core focus areas covered later in this module.
Storage Virtualization. EMC. 2009
Storage Virtualization
Storage Virtualization

56. Storage virtualization requires a multi-level approach
Copyright © 2009 EMC Corporation. Do not Copy - All Rights Reserved.
Storage virtualization requires a multi-level approach
Path management
Server
Volume management
Replication
Storage
Path redirection
Network
Load balancing - ISL trucking
Access control - Zoning
Volume management - LUNs
Access control
Storage
Replication
RAID
Storage Virtualization
Storage Virtualization. EMC. 2009
Storage Virtualization

57. Storage virtualization configuration
Copyright © 2009 EMC Corporation. Do not Copy - All Rights Reserved.
Storage virtualization configuration
Servers
Storage
Arrays
Virtualization
Appliance
Out-of-Band
(a)
Network
Servers
Storage
Arrays
In-Band
(b)
Network
Virtualization
Appliance
(a) In out-of-band implementation, the virtualized environment configuration is stored external to the data path
(b) The in-band implementation places the virtualization function in the data path
Storage Virtualization
Storage Virtualization. EMC. 2009
Storage Virtualization

58. Block-level storage virtualization
Copyright © 2009 EMC Corporation. Do not Copy - All Rights Reserved.
Block-level storage virtualization
Ties together multiple independent storage arrays
Presented to host as a single storage device
Mapping used to redirect I/O on this device to underlying physical arrays
Deployed in a SAN environment
Non-disruptive data mobility and data migration
Enable significant cost and resource optimization
Servers
Heterogeneous Storage Arrays
Virtualization Applied at SAN Level
Storage Virtualization
Storage Virtualization. EMC. 2009
Storage Virtualization

59. File-level virtualization
Copyright © 2009 EMC Corporation. Do not Copy - All Rights Reserved.
File-level virtualization
Every NAS device is an independent entity, physically and logically
Underutilized storage resources
Downtime caused by data migrations
NAS Devices/Platforms
Before File-Level Virtualization IP
Network
Storage
Array
File
Server
Clients
Break dependencies between end-user access and data location
Storage utilization is optimized
Nondisruptive migrations
NAS Devices/Platforms
After File-Level Virtualization IP
Network
Clients
Storage
Array
File
Server
Virtualization
Appliance
Storage Virtualization
Storage Virtualization. EMC. 2009
Storage Virtualization

60. How is storage virtualized at the enterprise level?
Currently Networks are virtualized using Metadata or Storage Volume Controllers. There are two types of network virtualization…
Metadata or Storage Volume Controllers are placed (out of band) outside the path of data flow.
Metadata or Storage Volume Controllers (SVC) are placed (in-band) or in the path of data flow.
Source: IBM Redbook Page 8