Fundamentals of stoorage

1. Unit III Backup and Recovery

2. Subtopic
o Backup Purpose -Disaster Recovery - Operational Backup –
Archival
o Backup Considerations
o Backup Granularity- Recovery Considerations,
o Backup Methods , Backup Process, Backup and Restore
Operations,
o Backup Topologies - Serverless Backup , Backup Technologies
-Backup to Tape - Physical Tape Library - Backup to Disk -
Virtual Tape Library

3. What is a Backup?
o Backup is an additional copy of data that can be used for
restore and recovery purposes
o The Backup copy is used when the primary copy is lost or
corrupted
o This Backup copy can be created by:
o Simply coping data (there can be one or more copies)
o Mirroring data (the copy is always updated with whatever is written to the
primary copy)

4. It’s All About Recovery
o Businesses back up their data to enable its recovery in case of
potential loss
o Businesses also back up their data to comply with regulatory
requirements
o Backup purposes:
o Disaster Recovery
o Restores production data to an operational state after disaster
o Operational
o Restore data in the event of data loss or logical corruptions that may occur
during routine processing
o Archival
o Preserve transaction records, email, and other business work products for
regulatory compliance

5. Backup/Recovery Considerations
o Customer business needs determine:
o What are the restore requirements – RPO & RTO?
o Where and when will the restores occur?
o What are the most frequent restore requests?
o Which data needs to be backed up?
o How frequently should data be backed up?
o hourly, daily, weekly, monthly
o How long will it take to backup?
o How many copies to create?
o How long to retain backup copies?

6. Other Considerations: Data
o Location
o Heterogeneous platform
o Local and remote
o Number and size of files
o Consider compression ratio
o Example:
o 10 files of 1MB size Vs 10000 files of 1KB size

7. Backup Granularity
Full Backup
Su Su Su Su Su
Incremental Backup
Su Su Su Su Su
M T T
W F S M T T
W F S M T T
W F S M T T
W F S
Cumulative (Differential) Backup
Su Su Su Su Su
M T T
W F S M T T
W F S M T T
W F S M T T
W F S
Amount of data backup

8. Restoring from Incremental Backup
o Key Features
o Files that have changed since the last backup are backed up
o Fewest amount of files to be backed up, therefore faster backup and less
storage space
o Longer restore because last full and all subsequent incremental backups must
be applied
Incremental
Tuesday
File 4
Incremental
Wednesday
Updated File 3
Incremental
Thursday
File 5 Files 1, 2, 3, 4, 5
Production
Friday
Files 1, 2, 3
Monday
Full Backup

9. Restoring from Cumulative Backup
o Key Features
o More files to be backed up, therefore it takes more time to backup
and uses more storage space
o Much faster restore because only the last full and the last cumulative
backup must be applied
Cumulative
Tuesday
File 4
Files 1, 2, 3
Monday
Full Backup Cumulative
Wednesday
Files 4, 5
Cumulative
Thursday
Files 4, 5, 6 Files 1, 2, 3, 4, 5, 6
Production
Friday

10. Backup Methods
o Cold or offline- In a cold backup, the application is not active
during the backup process.
o Hot or online- In a hot backup, the application is up and
running, with users accessing their data during the backup
process.
o Open file
o Retry
o Open File Agents

11. Backup Methods
o Point in Time (PIT) replica- copy method is deployed in
environments where the impact of downtime from a cold
backup or the performance resulting from a hot backup is
unacceptable.
o Bare metal recovery- refers to a backup in which all metadata,
system information, and application configurations are
appropriately backed up for a full system recovery.

12. Backup Architecture and Process
o Backup client
o Sends backup data to backup
server or storage node
o Backup server
o Manages backup operations
and maintains backup catalog
o Storage node
o Responsible for writing data to
backup device Backup Server/
Storage Node
Tape Library
Storage Array
Application Server/
Backup Client
Backup Data

13. Backup Operation
1
Application Server and Backup Clients
Backup Server Storage Node Backup Device
2
7
3b 4
5
3a
6
3a Backup server instructs storage node to
load backup media in backup device
Start of scheduled backup process
1
Backup server retrieves backup related
information from backup catalog
2
Backup server instructs backup clients to
send its metadata to the backup server
and data to be backed up to storage node
3b
Backup clients send data to storage node
4
Storage node sends data to backup device
5
Storage node sends media information to
backup server
6
Backup server update catalog and records
the status
7

14. Restore Operation
Application Server and Backup Clients
1
5
2
4
3
3
Backup Server Storage Node Backup Device
1 Backup server scans backup catalog
to identify data to be restore and the
client that will receive data
2 Backup server instructs storage node
to load backup media in backup device
3 Data is then read and send to backup
client
4 Storage node sends restore metadata
to backup server
5 Backup server updates catalog

15. Backup Topologies
o There are 3 basic backup topologies:
o Direct Attached Based Backup
o LAN Based Backup
o SAN Based Backup
o Mixed backup

16. Direct Attached Backups
Backup Device
Application Server
and Backup Client
and Storage Node
Backup Server
LAN
Metadata Data
In a direct-attached backup, a backup device is attached directly to the client.
Only the metadata is sent to the backup server through the LAN.
This configuration frees the LAN from backup traffic. The example shown in Figure
depicts use of a backup device that is not shared.
As the environment grows, however, there will be a need for central management of all
backup devices and to share the resources to optimize costs.
An appropriate solution is to share the backup devices among multiple servers.
In this example, the client also acts as a storage node that writes data on the backup
device.

17. LAN Based Backups
In LAN-based backup, all servers are connected to the LAN and all
storage devices are directly attached to the storage node (see Figure
in next slide).
The data to be backed up is transferred from the backup client
(source), to the backup device (destination) over the LAN, which may
affect network performance.
Streaming across the LAN also affects network performance of all
systems connected to the same segment as the backup server.
Network resources are severely constrained when multiple clients
access and share the same tape library unit (TLU).
This impact can be minimized by adopting a number of measures,
such as configuring separate networks for backup and installing
dedicated storage nodes for some application servers.

18. LAN Based Backups
LAN
Storage Node
Backup Device
Data
Application Server
and Backup Client Backup Server
Metadata

19. SAN Based Backups (LAN Free)
The SAN-based backup is also known as the LAN-free backup.
Figure in next slide also illustrates a SAN-based backup.
The SAN-based backup topology is the most appropriate solution
when a backup device needs to be shared among the clients.
In this case the backup device and clients are attached to the SAN.
In this example, clients read the data from the mail servers in the
SAN and write to the SAN attached backup device.
The backup data traffic is restricted to the SAN, and backup
metadata is transported over the LAN.
However, the volume of metadata is insignificant when compared to
production data. LAN performance is not degraded in this
configuration

20. SAN Based Backups (LAN Free)
Data
Metadata
Backup Device
Backup Server Application Server
and Backup Client
Storage Node
LAN FC SAN

21. Mixed Backup
The mixed topology uses both the LAN-based and SAN-based
topologies, as shown in Figure in next slide.
This topology might be implemented for several reasons, including
cost, server location, reduction in administrative overhead, and
performance considerations.

22. Mixed Backup
Data
Metadata
Backup Device
Backup Server Application Server
and Backup Client
Storage Node
LAN FC SAN
Application Server
and Backup Client
Metadata

23. Serverless backup
Serverless backup is a LAN-free backup methodology that does not
involve a backup server to copy data.
The copy may be created by a network-attached controller, utilizing
a SCSI extended copy or an appliance within the SAN.
These backups are called serverless because they use SAN
resources instead of host resources to transport backup data from
its source to the backup device, reducing the impact on the
application server.

24. Backup in NAS Environment – Server Based
The use of NAS heads imposes a new set of considerations on the
backup and recovery strategy in NAS environments.
In the NAS environment, backups can be implemented in four
different ways:
server based,
serverless,
or using Network Data Management Protocol (NDMP)
in either NDMP 2-way
or NDMP 3-way
In application server-based backup, the NAS head retrieves data
from storage over the network and transfers it to the backup client
running on the application server.
The backup client sends this data to a storage node, which in turn
writes the data to the backup device.
This results in overloading the network with the backup data and
the use of production (application) server resources to move backup
data.

25. Backup in NAS Environment – Server Based
NAS Head
Application Server
(Backup Client)
Backup Server/ Storage Node
Storage
Backup Device
Backup Request
Data
Metadata
LAN FC SAN

26. Backup in NAS Environment – Serverless
In serverless backup, the network share is mounted directly on
the storage node.
This avoids overloading the network during the backup process
and eliminates the need to use resources on the production
server.
In this scenario, the storage node, which is also a backup
client, reads the data from the NAS head and writes it to the
backup device without involving the application server.

27. Backup in NAS Environment – Serverless
NAS Head
Application Server
(Backup Client)
Backup Server /
Storage Node
Storage
Backup Device
Backup Request
Data
Metadata
LAN FC SAN

28. Backup in NAS Environment – NDMP 2-way
In NDMP, backup data is sent directly from the NAS head to the
backup device, while metadata is sent to the backup server.
In this model, network traffic is minimized by isolating data
movement from the NAS head to the locally attached tape
library.
Only metadata is transported on the network.
This backup solution meets the strategic need to centrally
manage and control distributed data while minimizing network
traffic.

29. Backup in NAS Environment – NDMP 2-way
NAS Head
Application Server
(Backup Client)
Backup Server
Storage
Backup Device
Backup Request
Data
Metadata
LAN FC SAN

30. Backing up a NAS Device – NDMP 3-way
In an NDMP 3-way file system, data is not transferred over the
public network.
A separate private backup network must be established between
all NAS heads and the “backup” NAS head to prevent any data
transfer on the public network in order to avoid any congestion or
affect production operations.
Metadata and NDMP control data is still transferred across the
public network.
NDMP 3-way is useful when you have limited backup devices in
the environment.
It enables the NAS head to control the backup device and share it
with other NAS heads by receiving backup data through NDMP.

31. Backing up a NAS Device – NDMP 3-way
NAS Head
Application Server
(Backup Client)
Backup Server
Backup Request
Data
Metadata
NAS Head
Storage
LAN
FC SAN
FC SAN
LAN
Backup Device

32. Backup Technology options
o Backup to Tape
o Physical tape library
o Backup to Disk
o Backup to virtual tape
o Virtual tape library

33. Backup to Tape
o Traditional destination for backup
o Low cost option
o Sequential / Linear Access
o Multiple streaming
o Backup streams from multiple clients to a single backup device
Tape
Data from
Stream 1 Data from
Stream 2 Data from
Stream 3

34. Physical Tape Library
Drives
Cartridges
Import/
Export
Mailbox
Linear
Robotics
System
Front View Back View
I/O Management Unit
Server Class Main Controller
Power Systems
Drives

35. Tape Limitations
o Reliability
o Restore performance
o Mount, load to ready, rewind, dismount times
o Sequential Access
o Cannot be accessed by multiple hosts simultaneously
o Controlled environment for tape storage
o Wear and tear of tape
o Shipping/handling challenges
o Tape management challenges

36. Backup to Disk
o Ease of implementation
o Fast access
o More Reliable
o Random Access
o Multiple hosts access
o Enhanced overall backup and recovery performance

37. Tape versus Disk – Restore Comparison
Typical Scenario:
 800 users, 75 MB mailbox
 60 GB database
Source: EMC Engineering and EMC IT
*Total time from point of failure to return of service to e-mail users
0 10 20 30 40 50 60 70 80 90 100 120
110
Recovery Time in Minutes*
Tape
Backup / Restore
Disk
Backup / Restore
108
Minutes
24
Minutes

38. Virtual Tape Library
Backup Server/
Storage Node
Backup Clients
Emulation Engine
Virtual
Tape
Library
Appliance
Storage (LUNs)
LAN
FC SAN

39. Tape Versus Disk Versus Virtual Tape
Tape
Disk-Aware
Backup-to-Disk
Virtual Tape
Offsite Capabilities Yes No Yes
Reliability
No inherent protection
methods
RAID, spare RAID, spare
Performance
Subject to mechanical
operations, load times
Faster single stream Faster single stream
Use Backup only
Multiple
(backup/production)
Backup only

40. Data De-duplication
o Data de-duplication refers to removal of redundant data. In the de-duplication
process, a single copy of data is maintained along with the index of the original
data, so that data can be easily retrieved when required. Other than saving disk
storage space and reduction in hardware costs, (storage hardware, cooling,
backup media, etc), another major benefit of data de-duplication is bandwidth
optimization.

41. Lesson Summary
Key points covered in this lesson:
o Backup topologies
o Direct attached, LAN and SAN based backup
o Backup in NAS environment
o Backup to Tape
o Backup to Disk
o Backup to virtual tape
o Comparison among tape, disk and virtual tape backup

42. Chapter Summary
Key points covered in this chapter:
o Backup and Recovery considerations and process
o Backup and Recovery operations
o Common Backup and Recovery topologies
o Backup technologies
o Tape, disk, and virtual tape

43. Check Your Knowledge
o What are three primary purposes for backup?
o What are the three topologies that support backup operation?
o Describe three major considerations of backup/recovery.
o What are the advantages and disadvantages in tape and virtual
tape backups?
o What are the three levels of granularity found in Backups?
o How backup is performed using virtual tape library?
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