- Management Reference Guide
- Table of Contents
- Introduction
- Strategic Management
- Establishing Goals, Objectives, and Strategies
- Aligning IT Goals with Corporate Business Goals
- Utilizing Effective Planning Techniques
- Developing Worthwhile Mission Statements
- Developing Worthwhile Vision Statements
- Instituting Practical Corporate Values
- Budgeting Considerations in an IT Environment
- Introduction to Conducting an Effective SWOT Analysis
- IT Governance and Disaster Recovery, Part One
- IT Governance and Disaster Recovery, Part Two
- Customer Management
- Identifying Key External Customers
- Identifying Key Internal Customers
- Negotiating with Customers and Suppliers—Part 1: An Introduction
- Negotiating With Customers and Suppliers—Part 2: Reaching Agreement
- Negotiating and Managing Realistic Customer Expectations
- Service Management
- Identifying Key Services for Business Users
- Service-Level Agreements That Really Work
- How IT Evolved into a Service Organization
- FAQs About Systems Management (SM)
- FAQs About Availability (AV)
- FAQs About Performance and Tuning (PT)
- FAQs About Service Desk (SD)
- FAQs About Change Management (CM)
- FAQs About Configuration Management (CF)
- FAQs About Capacity Planning (CP)
- FAQs About Network Management
- FAQs About Storage Management (SM)
- FAQs About Production Acceptance (PA)
- FAQs About Release Management (RM)
- FAQs About Disaster Recovery (DR)
- FAQs About Business Continuity (BC)
- FAQs About Security (SE)
- FAQs About Service Level Management (SL)
- FAQs About Financial Management (FN)
- FAQs About Problem Management (PM)
- FAQs About Facilities Management (FM)
- Process Management
- Developing Robust Processes
- Establishing Mutually Beneficial Process Metrics
- Change Management—Part 1
- Change Management—Part 2
- Change Management—Part 3
- Audit Reconnaissance: Releasing Resources Through the IT Audit
- Problem Management
- Problem Management–Part 2: Process Design
- Problem Management–Part 3: Process Implementation
- Business Continuity Emergency Communications Plan
- Capacity Planning – Part One: Why It is Seldom Done Well
- Capacity Planning – Part Two: Developing a Capacity Planning Process
- Capacity Planning — Part Three: Benefits and Helpful Tips
- Capacity Planning – Part Four: Hidden Upgrade Costs and
- Improving Business Process Management, Part 1
- Improving Business Process Management, Part 2
- 20 Major Elements of Facilities Management
- Major Physical Exposures Common to a Data Center
- Evaluating the Physical Environment
- Nightmare Incidents with Disaster Recovery Plans
- Developing a Robust Configuration Management Process
- Developing a Robust Configuration Management Process – Part Two
- Automating a Robust Infrastructure Process
- Improving High Availability — Part One: Definitions and Terms
- Improving High Availability — Part Two: Definitions and Terms
- Improving High Availability — Part Three: The Seven R's of High Availability
- Improving High Availability — Part Four: Assessing an Availability Process
- Methods for Brainstorming and Prioritizing Requirements
- Introduction to Disk Storage Management — Part One
- Storage Management—Part Two: Performance
- Storage Management—Part Three: Reliability
- Storage Management—Part Four: Recoverability
- Twelve Traits of World-Class Infrastructures — Part One
- Twelve Traits of World-Class Infrastructures — Part Two
- Meeting Today's Cooling Challenges of Data Centers
- Strategic Security, Part One: Assessment
- Strategic Security, Part Two: Development
- Strategic Security, Part Three: Implementation
- Strategic Security, Part Four: ITIL Implications
- Production Acceptance Part One – Definition and Benefits
- Production Acceptance Part Two – Initial Steps
- Production Acceptance Part Three – Middle Steps
- Production Acceptance Part Four – Ongoing Steps
- Case Study: Planning a Service Desk Part One – Objectives
- Case Study: Planning a Service Desk Part Two – SWOT
- Case Study: Implementing an ITIL Service Desk – Part One
- Case Study: Implementing a Service Desk Part Two – Tool Selection
- Ethics, Scandals and Legislation
- Outsourcing in Response to Legislation
- Supplier Management
- Identifying Key External Suppliers
- Identifying Key Internal Suppliers
- Integrating the Four Key Elements of Good Customer Service
- Enhancing the Customer/Supplier Matrix
- Voice Over IP, Part One — What VoIP Is, and Is Not
- Voice Over IP, Part Two — Benefits, Cost Savings and Features of VoIP
- Application Management
- Production Acceptance
- Distinguishing New Applications from New Versions of Existing Applications
- Assessing a Production Acceptance Process
- Effective Use of a Software Development Life Cycle
- The Role of Project Management in SDLC— Part 2
- Communication in Project Management – Part One: Barriers to Effective Communication
- Communication in Project Management – Part Two: Examples of Effective Communication
- Safeguarding Personal Information in the Workplace: A Case Study
- Combating the Year-end Budget Blitz—Part 1: Building a Manageable Schedule
- Combating the Year-end Budget Blitz—Part 2: Tracking and Reporting Availability
- References
- Developing an ITIL Feasibility Analysis
- Organization and Personnel Management
- Optimizing IT Organizational Structures
- Factors That Influence Restructuring Decisions
- Alternative Locations for the Help Desk
- Alternative Locations for Database Administration
- Alternative Locations for Network Operations
- Alternative Locations for Web Design
- Alternative Locations for Risk Management
- Alternative Locations for Systems Management
- Practical Tips To Retaining Key Personnel
- Benefits and Drawbacks of Using IT Consultants and Contractors
- Deciding Between the Use of Contractors versus Consultants
- Managing Employee Skill Sets and Skill Levels
- Assessing Skill Levels of Current Onboard Staff
- Recruiting Infrastructure Staff from the Outside
- Selecting the Most Qualified Candidate
- 7 Tips for Managing the Use of Mobile Devices
- Useful Websites for IT Managers
- References
- Automating Robust Processes
- Evaluating Process Documentation — Part One: Quality and Value
- Evaluating Process Documentation — Part Two: Benefits and Use of a Quality-Value Matrix
- When Should You Integrate or Segregate Service Desks?
- Five Instructive Ideas for Interviewing
- Eight Surefire Tips to Use When Being Interviewed
- 12 Helpful Hints To Make Meetings More Productive
- Eight Uncommon Tips To Improve Your Writing
- Ten Helpful Tips To Improve Fire Drills
- Sorting Out Today’s Various Training Options
- Business Ethics and Corporate Scandals – Part 1
- Business Ethics and Corporate Scandals – Part 2
- 12 Tips for More Effective Emails
- Management Communication: Back to the Basics, Part One
- Management Communication: Back to the Basics, Part Two
- Management Communication: Back to the Basics, Part Three
- Asset Management
- Managing Hardware Inventories
- Introduction to Hardware Inventories
- Processes To Manage Hardware Inventories
- Use of a Hardware Inventory Database
- References
- Managing Software Inventories
- Business Continuity Management
- Ten Lessons Learned from Real-Life Disasters
- Ten Lessons Learned From Real-Life Disasters, Part 2
- Differences Between Disaster Recovery and Business Continuity , Part 1
- Differences Between Disaster Recovery and Business Continuity , Part 2
- 15 Common Terms and Definitions of Business Continuity
- The Federal Government’s Role in Disaster Recovery
- The 12 Common Mistakes That Cause BIAs To Fail—Part 1
- The 12 Common Mistakes That Cause BIAs To Fail—Part 2
- The 12 Common Mistakes That Cause BIAs To Fail—Part 3
- The 12 Common Mistakes That Cause BIAs To Fail—Part 4
- Conducting an Effective Table Top Exercise (TTE) — Part 1
- Conducting an Effective Table Top Exercise (TTE) — Part 2
- Conducting an Effective Table Top Exercise (TTE) — Part 3
- Conducting an Effective Table Top Exercise (TTE) — Part 4
- The 13 Cardinal Steps for Implementing a Business Continuity Program — Part One
- The 13 Cardinal Steps for Implementing a Business Continuity Program — Part Two
- The 13 Cardinal Steps for Implementing a Business Continuity Program — Part Three
- The 13 Cardinal Steps for Implementing a Business Continuity Program — Part Four
- The Information Technology Infrastructure Library (ITIL)
- The Origins of ITIL
- The Foundation of ITIL: Service Management
- Five Reasons for Revising ITIL
- The Relationship of Service Delivery and Service Support to All of ITIL
- Ten Common Myths About Implementing ITIL, Part One
- Ten Common Myths About Implementing ITIL, Part Two
- Characteristics of ITIL Version 3
- Ten Benefits of itSMF and its IIL Pocket Guide
- Translating the Goals of the ITIL Service Delivery Processes
- Translating the Goals of the ITIL Service Support Processes
- Elements of ITIL Least Understood, Part One: Service Delivery Processes
- Case Study: Recovery Reactions to a Renegade Rodent
- Elements of ITIL Least Understood, Part Two: Service Support
- Case Studies
- Case Study — Preparing for Hurricane Charley
- Case Study — The Linux Decision
- Case Study — Production Acceptance at an Aerospace Firm
- Case Study — Production Acceptance at a Defense Contractor
- Case Study — Evaluating Mainframe Processes
- Case Study — Evaluating Recovery Sites, Part One: Quantitative Comparisons/Natural Disasters
- Case Study — Evaluating Recovery Sites, Part Two: Quantitative Comparisons/Man-made Disasters
- Case Study — Evaluating Recovery Sites, Part Three: Qualitative Comparisons
- Case Study — Evaluating Recovery Sites, Part Four: Take-Aways
- Disaster Recovery Test Case Study Part One: Planning
- Disaster Recovery Test Case Study Part Two: Planning and Walk-Through
- Disaster Recovery Test Case Study Part Three: Execution
- Disaster Recovery Test Case Study Part Four: Follow-Up
- Assessing the Robustness of a Vendor’s Data Center, Part One: Qualitative Measures
- Assessing the Robustness of a Vendor’s Data Center, Part Two: Quantitative Measures
- Case Study: Lessons Learned from a World-Wide Disaster Recovery Exercise, Part One: What Did the Team Do Well
- (d) Case Study: Lessons Learned from a World-Wide Disaster Recovery Exercise, Part Two
The other critical characteristic of storage management is reliability. As companies, and individuals, save more and more of their crucial information on storage devices, the need to be able to retrieve it quickly, and in the identical format from which it was saved, becomes ever more urgent. But this need for reliable disk storage is not new. This emphasis on reliability can be illustrated with a highly publicized anecdote involving IBM that occurred some 25 years ago.
IBM had always been proud that it had never missed a first customer ship date for any major product in the company's history. In late 1980, it announced an advanced new disk drive, the model 3380, with a first customer ship date of October 1981. Anticipation was high because this model would have tightly packed tracks with densely packed data, providing record storage capacity at an affordable price.
While performing final lab testing in the summer of 1981, engineers discovered that, under extremely rare conditions, the redundant power supply in the new model drive could intermittently malfunction. If another set of conditions occurred at the same time, a possible write error could result. A team of engineering specialists studied the problem for weeks but could not consistently duplicate the problem, which was necessary to enable a permanent fix. A hotly contested debate ensued within IBM about whether or not to delay shipment until the problem could be satisfactorily resolved, with each side believing that the opposing position would do irreparable damage to the corporation.
The decision went to the highest levels of IBM management who decided they could not undermine the quality of their product or jeopardize the reputation of their company by adhering to an artificial schedule with a suspect offering. In August, IBM announced it was delaying general availability of its model 3380 disk drive system for at least three months, and longer if necessary. Wall Street, industry analysts, and interested observers held their collective breath, expecting major fallout from the announcement. It never came.
Customers were more impressed than disappointed by IBM's acknowledgment of the criticality of disk drive reliability. Within a few months the problem was traced to a power supply filter not being able to handle rare voltage fluctuations. It was estimated at the time that the typical shop using clean, or conditioned, power had less than a one-in-a-million chance of ever experiencing the set of conditions required to trigger the malfunction.
The episode served to strengthen the notion of just how important reliable disk equipment had become. With companies beginning to run huge corporate databases on which the success of their business often depended, data storage reliability was of prime concern. Manufacturers began designing into their disk storage systems redundant components such as backup power systems, dual channel ports to disk controllers, and dual pathing between drives and controllers. These improvements significantly increased the reliability of disk and tape storage equipment, in some instances more than doubling the usual one-year mean time between failures (MTBF) for a disk drive. Even with this improved reliability, the drives were far from fault tolerant. If a shop had 100 disk drives—not uncommon at that time—it could expect an average failure rate of one disk drive per week.
Fault-tolerant systems began appearing in the 1980s, a decade in which entire processing environments were duplicated in a hot standby mode. These systems essentially never went down, making their high cost justifiable for many manufacturing companies with large, 24-hour workforces, who needed processing capability but not much in the way of databases.Most of the cost was in the processing part since databases were relatively small and disk storage requirements low. However, there were other types of companies that had large corporate databases requiring large amounts of disk storage. The expense of duplicating huge disk farms all but put most of them out of the running for fault-tolerant systems.
RAID Technology
During this time, technological advances in design and manufacturing drove down the expense of storing data on magnetic devices. By the mid-1980s, the cost per megabyte of disk storage had plummeted to a fraction of what it had been a decade earlier. Smaller, less reliable disks such as those on PCs were less expensive still. But building fault-tolerant disk drives was still an expensive proposition due to the complex software needed to run high-capacity disks in a hot standby mode in concert with the operating system. Manufacturers then started looking at connecting huge arrays of small, slightly less reliable and far less expensive disk drives and operating them in a fault-tolerant mode that was basically independent of the operating systems on which they ran. This was accomplished by running a separate drive in the array for parity bits.
This type of disk configuration was called a redundant array of inexpensive disks, or RAID. By the early 1990s most disk drives were considered inexpensive, moving the RAID Advisory Board to officially change the I in RAID to independent rather than inexpensive. Advances and refinements led to improvements in affordability, performance, and especially reliability. Performance was improved by disk striping, which writes data across multiple drives, increasing data paths and transfer rates and allowing simultaneous reading and writing to multiple disks. This implementation of RAID is referred to as level 0. Reliability was improved through mirroring (level 1) or use of parity drives (level 3 or 5). The result is that RAID has become the de facto standard for providing highly reliable disk storage systems to mainframe, midrange and client-server platforms. Table 1 lists the five most common levels of RAID.
Table 1 RAID Level Descriptions
|
RAID Level |
Explanation |
|
0 |
Disk striping for performance reasons |
|
1 |
Mirroring for total redundancy |
|
0+1 |
Combination of striping and mirroring |
|
3 |
Striping and fault tolerance with parity on totally dedicated parity drives |
|
5 |
Striping and fault tolerance with parity on non-associated data drives |
Mirroring at RAID level 1 means that all data is duplicated on separate drives so that if one drive malfunctions its mirrored drive maintains uninterrupted operation of all read and write transactions. Software and microcode in the RAID controller take the failing drive offline and issue messages to appropriate personnel to replace the drive while the array is up and running. More sophisticated arrays notify a remote repair center and arrange replacement of the drive with the supplier with little or no involvement of infrastructure personnel. This level offers virtually continuous operation of all disks.
The combination of striping and mirroring goes by several nomenclatures including:
- 0,1
- 0 plus 1
- 0+1.
As its various names suggest, this level of RAID duplicates all data for high reliability and stripes the data for high performance.
RAID level 3 stripes the data for performance reasons similar to RAID level 0 and, for high reliability, assigns a dedicated parity drive on which parity bits are written to recover and rebuild data in the event of a data drive malfunction. There are usually two to four data drives supported by a single parity drive.
RAID level 5 is similar to level 3 except that parity bits are shared on non-associated data drives. For example, for three data drives labeled A, B, and C, the parity bits for data striped across drives B and C would reside on drive A; the parity bits for data striped across drives A and C would reside on drive B; the parity bits for data striped across drives A and B would reside on drive C.
Selecting Products and Vendors Best for You
A general knowledge about how an application accesses data can help in determining which level of RAID to employ. For example, the relatively random access into the indexes and data files of a relational database make them ideal candidates for RAID 0+1. The sequential nature of log files would make them better candidates for just RAID 1 alone. By understanding the different RAID levels, storage management process owners can better evaluate which scheme is best suited for their business goals, their budgetary targets, their expected service levels, and their technical requirements.
In recent years, several manufacturers have advanced RAID technology. I have worked with EMC's Clariion (midrange) and Symmetrix (high range) models and both have proven track records for performance and reliability. Costs and marketing supporting are sometimes an issue with EMC. I also have experience with IBM's large capacity storage devices. The so-called IBM Shark disk array can scale up to almost 200 terabytes and uses it cache and RAID technology very effectively to deliver excellent performance and reliability. As with any major hardware purchase, requirements should be compiled and prioritized to select the best storage vendor for your particular environment
In the upcoming part four of this series, I will discuss another key element of disk storage; recoverability. With so much emphasis these days on business continuity and disaster recovery, this aspect of storage management will tie it to several current management issues.