Comp8 unit9b lecture_slides

1. Installation and Maintenance of Health
IT Systems
Creating Fault-Tolerant Systems,
Backups, and Decommissioning
Lecture b
This material (Comp 8 Unit 9) was developed by Duke University, funded by the Department of Health and
Human Services, Office of the National Coordinator for Health Information Technology under Award
Number IU24OC000024. This material was updated in 2016 by The University of Texas Health Science
Center at Houston under Award Number 90WT0006.
This work is licensed under the Creative Commons Attribution-NonCommercial-ShareAlike 4.0 International
License. To view a copy of this license, visit http://creativecommons.org/licenses/by-nc-sa/4.0/.

2. Creating Fault-Tolerant Systems,
Backups, and Decommissioning
Learning Objectives
1. Define availability, reliability, redundancy, and fault
tolerance (Lecture a)
2. Explain areas and outline rules for implementing fault
tolerant systems (Lecture a)
3. Perform risk assessment (Lecture a)
4. Follow best practice guidelines for common
implementations (Lecture b)
5. Develop strategies for backup and restore of operating
systems, applications, configuration settings, and
databases (Lecture c)
6. Decommission systems and data (Lecture c)
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3. Creating Fault Tolerance:
Computer Hardware
• Redundant and fault tolerant hardware costs more
• Computers are workstations and servers
– Workstations need little fault tolerance
o No critical data – used interchangeably
– Servers need redundancy and fault tolerance
o Hot-swap hard drives
o Hot-plug expansion cards
o Error checking and correcting, hot-add memory
o Redundant and hot-swap fans
o Redundant power supply (PSU)
– Multiple servers
o Clustered systems are complex but highly available
o Mirrored servers less complex but highly available
o Hot spare simplest configuration but requires effort after failure
(Tulloch, 2005)
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4. Creating Fault Tolerance:
Data Storage
Store data redundantly, so that single failures cause no loss
• RAID (Redundant Array of Independent Disks) for hard drives
– RAID 0 provides no fault tolerance! Speed increase only
– RAID 1 (disk mirroring): Fast reading, simple, easy
– RAID 5 (disk striping with distributed parity): increased
speed & reliability with relatively few disks, complex
o Critical systems should include a hot spare
– RAID 6 (disk striping with double distributed parity):
increased speed & additional reliability with relatively few
disks, similar to RAID 5 in complexity
(Tulloch, 2005; RAID, 2012)
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5. Example RAID Arrays
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6. Creating Fault Tolerance:
Data Storage (cont’d)
Store data redundantly, so that single failures cause no loss
• Distributed file system running over a network
– Distributed File System (DFS) for Windows
o Used with File Replication Service (FRS) to duplicate data
– Others will depend on platform, can include ZFS (Solaris), AFS (general UNIX),
GFS (RedHat)
– SAN (Storage Area Network), NAS (Network Attached Storage)
o EMC2 and NetApp are large vendors
– Cloud or Hosted storage uses the Internet
o Let someone else worry about drives!
o Dropbox
o iCloud
o Amazon S3
o Windows Azure Storage
(Tulloch, 2005)
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7. Creating Fault Tolerance:
Virtualization
• Types of Virtualization
– Storage virtualization – discussed previously
– Server virtualization - virtual machines (VMs)
o Virtual Machine = Software emulation of physical environment
o Server running VMs called a VM host – multiple VMs run on single host
o Advantages
 Easy upgrading and scalability
 Simplified hardware management and fault tolerance
 Easy to integrate existing systems and infrastructure
o Disadvantage is a slight performance hit and more systems down with failure
o Some services, e.g. Databases not perfectly suited for virtualization
 Best practices for each service are available from the service vendor.
– Infrastructure virtualization
o Everything accessed through remote interfaces
o Contracted level of service is important to specify
o Simple devices + Internet access = Infrastructure as a Service (IaaS)
(Sanford, 2010)
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8. Creating Fault Tolerance:
Off-Site Hosting and Access
Hosted servers are similar to hosted storage, but can maintain
an entire environment.
• Web server hosting is early example
• Virtual Servers “in the cloud”
– System hardware extremely reliable and fault tolerant,
backed by service guarantees.
• Ensure availability for servers with:
– Redundancy & fault tolerance in network infrastructure:
o Switches with Spanning Tree
o Routers with secondary or backup links
o Multiple Internet connections: Multihoming
– Uninterruptible Power Supply (UPS) & backup power in
key areas, e.g. server rooms, wiring closets, critical PCs
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9. Creating Fault Tolerance:
Software as a Service (SaaS)
• SaaS, also known as Application Service Provider (ASP) or
Cloud provider
• Benefits:
– No local hardware admin costs (except network access)
– Service contract guarantees very high fault tolerance
– Accessible from PCs, tablets – potentially anything with a
web browser
• Drawbacks
– Cost grows as usage grows – not a fixed cost
– Network access can fail – whose fault is it?
o Internet Access Provider
o SaaS Host Provider
o SaaS Company or software
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10. Creating Fault-Tolerant Systems,
Backups, and Decommissioning
Summary – Lecture b
• Best Practices for providing fault tolerant
computer hardware, data storage,
virtualization, remote hosting, and network
access
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11. Creating Fault-Tolerant Systems,
Backups, and Decommissioning
References – Lecture b
References
RAID [cited 2012 January 31]. Retrieved from: http://en.wikipedia.org/wiki/RAID
Sanford, R. (April 2010) Electronic Health Records Need a Fail-Proof Foundation to Deliver on Quality,
Economy Promises.” Health News Digest. Available from:
http://www.healthnewsdigest.com/news/Guest_Columnist_710/Electronic_Health_Records_Need_
a_Fail-Proof_Foundation_to_Deliver_on_Quality_Economy_Promises_2_printer.shtml
Shackhow, T. et al. (June 2008). EHR Meltdown: How to Protect Your Patient Data. Fam Pract Manag,
15(6), A3-A8. Available from: http://www.aafp.org/fpm/2008/0600/pa3.html
Tulloch, M. (April 2005) “Implementing Fault Tolerance on Windows Networks”. Available from:
http://www.windowsnetworking.com/articles_tutorials/Implementing-Fault-Tolerance-Windows-
Networks.html
Images
Slide 5: RAID 0, RAID 1, RAID 5, RAID 6 [en:User:Cburnett]. c2006 [updated 2000 Jan 28; cited 2006
Feb 15]. Available from:
http://commons.wikimedia.org/wiki/Redundant_array_of_independent_disks
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12. Installation and Maintenance of
Health IT Systems
Creating Fault-Tolerant Systems,
Backups, and Decommissioning
Lecture b
This material was developed by Duke University,
funded by the Department of Health and Human
Services, Office of the National Coordinator for
Health Information Technology under Award
Number IU24OC000024. This material was
updated in 2016 by The University of Texas Health
Science Center at Houston under Award Number
90WT0006.
12