Chapter 13 sets a new level for our author being oblivious. Its opening pages discuss much of the destruction that was caused by Hurricane Katrina in 2005 in Florida, Mississippi, Georgia, and Alabama. These pages also ignore the damage this hurricane caused in the state of Louisiana, specifically to the city of New Orleans. Are those victims of the storm so well known that he thought he only needed to mention the other states? A better discussion is on Wikipedia, at the link provided.
Once we are past the author's omission, we may consider his remarks about the effects of a disaster that might be reduced by detailed planning and action based on such planning.
The first threat considered is fire. Some statistics are given and the author presents a list of four elements that must be present for a fire to exist. His fourth element is the fire itself, so it does not belong on the list. The other three are those we discussed in class earlier in the term.
For a fire to exist, three factors are needed:
If you can eliminate any one of these factors, the fire will go out. This is why Carbon Dioxide extinguishers work: the CO2 replaces the oxygen in the immediate vicinity of a fire, and the fire stops. Smothering a campfire works about the same way.
A fire break is an example of fighting a fire by depriving it of fuel. Forest fires can be fought this way. Somewhat similarly, I once walked into a rest room in an office and found that someone had placed a roll of toilet paper on top of the light fixture over the sink. I noticed it because it was on fire. I grabbed the roll of paper and tossed it into the sink. This established a fire break between the fire and the rest of the building. I then put out the fire on the roll of paper with water (depriving it of oxygen).
Keeping your computer system cool, so that a fire will not ignite, is your most effective form of firefighting: don't let it start.
Fire Extinguishers - Fire extinguishers are classed by the kind of fire they are able to put out. The links below will take you to sites with more information about fire classes and extinguishers. In surveying several sites, I found that there are currently at least four classes of fires, and that the symbols for them have been updated to use pictures instead of letters. Some sites list a Class K for cooking oils (Kitchen fires), but this does not seem to be universal. The chart below contains American symbols:
Information from FEMA
Information from Underwriters Laboratories
Information from the University of Oklahoma Police Department
The table below is from a Wikipedia article on fire classes. It shows that the same kind of fire is called by a different name in different places:
In most cases, a multiclass extinguisher is preferred. On extinguishers I examined at my workplace, multiple picture symbols were used, showing the pictures for classes A, B, and C.
The text discusses the fact that all kinds of electrical equipment radiate electrons to one degree or another. In this section it is important to know a few facts.
The text discusses some ideas about heating, ventilation, and air conditioning, which include some concerns about humidity. Why do we care about humidity? It inhibits ESD (Electrostatic Discharge).
Static electricity - ESD, or Electrostatic Discharge, can be a serious cause of problems. Some numbers from a previous text may help you understand the situation:
The damage from low voltage may not cause immediate failure so you may never know the cause of the failure that eventually happens.
Servers are often set up in a cluster, a group of servers that provide services redundantly. If one of the servers in a cluster goes down, the other (or others) provide the services the down server would have provided. The text lists two types of clusters:
The text discusses RAID, which has been defined several ways. Eventually, all hard drives fail, and RAID allows a system to continue in most cases. One common meaning is Redundant Array of Independent Drives. The word "independent" seems unnecessary, and is in fact misleading. Hard drives set up in a RAID array perform functions that relate to each other. Several kinds of RAID exist to provide for redundant storage of data or to provide for a means to recover lost data. The text discusses four types. Follow the link below to a nice summary of RAID level features not listed in these notes, as well as helpful animations to show how they work. Note that RAID 0 does not provide fault tolerance, the ability to survive a device failure.
The text mentions that some entities need redundant connections to and through networks. It does not give specific details about this concept.
Power can be supplied to a computer system through an Uninterruptible Power Supply (UPS) that is essentially a smart battery that kicks in when the main power is lost. The text describes two kinds of UPS:
The off-line (standby) model has a short lag time in the event of a power loss before the battery circuit starts working. The on-line (inline) model does not have this lag time. A typical UPS works with software that detects a power loss and alerts administrators when it occurs. Depending on the capacity of the UPS and the load placed on it, it may allow operation for hours, for minutes, or only long enough to perform a shut down of the system it is protecting.
Backup generators are typical in large installations, such as data centers that support a large population or enterprise.
In the case of a disaster that makes a work site unusable, such as a fire or flood, it becomes necessary to have a plan for alternate means of continuing business. The text lists three types of off site operation plans:
The definitions of hot, warm, and cold sites vary between sources, but the basic idea is always the same. The three types of sites provide different levels of service and different time frames in which you would be ready to resume business. Obviously, the hot site is best but it requires the most money and effort to maintain. The cold site is cheapest, but it has additional costs that will be added as soon as you need to use it.
Disaster Recovery Procedures
The previous section was about what could be done while a disaster is occurring. Disaster recovery can be more about what to do once the disaster is over. The text divides this concept into three sections: planning, exercises, and data backup.
Although a disaster recovery plan is used after the disaster, it should be made well before a disaster occurs. The text provides a general outline that a formal Disaster Recovery Plan document might follow. You should look over the sections of the model in the text. Most of the items in it are those that have been discussed already.
Testing the disaster plan is the purpose of a disaster exercise. It should be carried out regularly, and the outcome of the exercise should be examined to determine what updates need to be made to the plan.
Four backup strategies, or schedules, are explained. You should
know them. First some terms:
This needs more explanation. Assume we use a tape drive to make backups. In a Full backup strategy, the entire target is backed up to tape every time we make a backup tape. This strategy consumes the most time and the most tapes to carry out a backup. To restore, we simply restore the most recent tape(s). This is the least time consuming strategy for restoring, but the most time consuming for creating backups.
The second method, Incremental backup, means that we start with a Full backup of the target, and then each successive backup tape we create only backs up the elements that are new or changed since the last backup was created. This means that successive backups will not always be the same length. Therefore, this is the least time consuming backup, but the most time consuming restore. To restore, we must first restore the last Full backup made, and then restore EVERY tape made since then, to ensure getting all changes.
The third strategy, Differential backup, also starts with a Full backup tape. Then each successive tape made will contain all the files changed since the last Full backup was made. This means that we will have to restore only one or two tapes in a restore operation. If the last tape made was a Full tape, we restore only that one. If the last tape made was a Differential tape, we restore the last Full tape, then the last Differential tape.
The fourth strategy, Copy, is no different from Full in terms of backup or restore time. In both Incremental and Differential backup strategies, you will typically use a rotation schedule. For example, you could have a one week cycle. Once a week, you make a Full backup, then every day after that you make the other kind you have chosen to use: Incremental or Differential.
To keep them straight in your mind, remember that:
The time required to create backup tapes should be considered along with the time to restore a backup. When you consider the two concepts as two sides of the answer to a question (What method should I use?), the answer may be the most common choice: Differential. It is the best compromise in terms of backup time versus restore time. Note also, that all three standard methods require a full backup on a regular cycle. The recommendation is usually to run a Full backup tape weekly.
The discussion above assumes that your backups are being written to tapes, which has been the most common method for many years. The text discusses three other methods, each requiring different hardware. Copying to other drives is faster, but only if connected by a fast channel, such as being in the same computer. This leads to a problem of removing the copy from the same location as the original. Copying to a disk in another data center is possible, and fast if they are connected by fiber, but costly in terms of setup.
Incident Response Procedures
An incident can be an event of any sort, but some texts, ours included, call an incident an event caused by an attack. The last five pages of the chapter concern the actions that should be taken when an incident has been detected.
A forensic investigation is typically one that concerns a crime. This section is about computer forensics, investigations into crimes that involve computers and other information system equipment. The text discusses four aspects of an investigation:
The text elaborates on memory and storage locations that should be examined for meaningful data. What you can expect to find there may surprise you: