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476 Part VII ✦ Disaster Recovery Backup hardware There are also many different kinds of backup hardware. You can choose tape stackers, libraries and autoloaders, and jukeboxes. Each of these types of backup hardware has a different purpose, and function. The sections that follow discuss some of the hardware types that you can choose from. Tape stackers A tape stacker is a sequential access device that uses tapes in the order they are loaded in the changer. If an operation exceeds the limits of a tape, the stacker con- tinues the operation onto the next tape, and so on, until all the data is backed up. You must have the tapes inserted in the correct order, or you run into problems. Stackers work best in a single-system backup, where there is less confusion about the order of the tapes. They are less suitable for certain restore operations, such as those where files may be restored at random. Stackers are very common in main- frame applications. Libraries and autoloaders Tape libraries and autoloaders are more complex and more sophisticated than stackers. A library device will allow any one of the tapes to be loaded into the drive. Most library devices use multiple drives for parallel reading and writing operations. Because these devices are based on a random-access principle, you can load the tapes in any order that you want, as the device will make the necessary adjust- ments and ensure the media is used correctly. Libraries also make it easier to access files for restoration, as any one of the media can be easily accessed. Some library systems enable end users to perform medial tasks such as restoring files that they accidentally deleted. This type of machines can also be set up for auto- mated tape cleaning. When the tape-cleaning cartridge is loaded into the drive, the cleaning will be automatically triggered. However, remember to replace these tapes based on the tape manufactures suggested capabilities. Jukeboxes Jukeboxes are typically used in conjunction with optical media. Jukeboxes are like libraries in the sense that they use the same random-access methodology. Jukeboxes can read and restore data far faster than their tape counterparts, and this reason makes them invaluable to many companies. Jukeboxes are excellent choices for near-line storage components used in archival schemes. Near-line storage is used by data warehouses as an inexpensive, scalable way to store large volumes of data. Near-line storage devices include DAT, DLT tapes (sequential access), CD-ROMs, DVD-ROMs, DVD-RAMs, and Magneto-Optical (random access) devices. Retrieval of data can be slow, but the type of data (archives, past records, etc.) dictates that the information will not be accessed often. Exam Tip 4809-3 ch19.F 5/15/01 9:50 AM Page 476 477 Chapter 19 ✦ Backing Up and Restoring Maintenance To achieve peak performance for your tape drive, you must follow the manufac- tures suggested schedule for cleaning. If you cannot find the manufacturer’s specifi- cations, the general rule is to clean the tape after every 30 hours of use. If you can’t keep track of the hours each tape has been used, you should try to do this three or four times per month. The tape heads act like a magnet, and airborne particles get attached to the heads. This greatly reduces the drive’s efficiency and reliability, which could result in read/write errors when trying to perform a backup or restore operation. The other problem is that the tapes themselves can flake off dirt parti- cles onto the heads. Simply reading and writing tapes makes the drive heads dirty. You may start to get an increase in tape head errors from the tape backup system if the heads are badly damaged or dirty. If this happens, try cleaning the heads sev- eral times, and then use a brand-new tape for the next backup. If you still see the errors, you may need to replace the tape heads. This is often an expensive proce- dure, and hopefully the warranty is still in effect. If not, you may opt to purchase a new unit. If you have tapes that sit around for extended periods of time, you should exercise the tape at least once per year. Most backup systems have a procedure for doing this, but it is a simply procedure of reading data to the end of the tape and then rewinding it. This will ensure that the tape remains flexible and reliable. Types of Backups ✦ Identify types of backup and restoration schemes Part of forming your backup strategy is deciding what to back up. Sometimes you need to back up all the data on a certain device. However, if only ten percent of the files on that device have changed since the last time it was backed up, backing up all the files is a waste of time. In this case, you would only want to back up the files that have changed. The following sections detail several methods to help you achieve an efficient backup plan. Each file has a special bit called the archive bit. When a file is changed, the archive bit is set to indicate that the file has been changed, and should be backed up. Some types of backups reset the archive bit, indicating that the file has been backed up, and is safe until the next time the file is changed. Full backup In a full backup, you back up all the files on all the selected devices. It would be ideal to perform a full backup every time. However, because of the size of a typical full backup, and the time required to execute one, it may be impractical to do so. A full backup resets the archive bit on every file that is backed up. Objective 4809-3 ch19.F 5/15/01 9:50 AM Page 477 478 Part VII ✦ Disaster Recovery The advantages of a full backup are: ✦ A full backup contains all the system’s data on the media. ✦ If you must restore a full volume, the recovery time is shorter. ✦ Files are easier to locate because backups include all the data contained on the device. The disadvantages of this method are: ✦ Backups become redundant because the majority of files rarely change. ✦ Full backups take longer and can require more media. This increases as more devices are added. Incremental backup An incremental backup captures all the files that have changed since last full or incremental backup The archive bit is switched off so the files will appear to the system as having been backed up. To restore the full volume, you must first restore from the last full backup, and then apply each of the incremental backups. To exe- cute this effectively, you should plan to have current full backups on hand that go with the incremental ones. Suppose, you perform a full backup on Saturday, and incremental backup on Monday through Friday. If the system fails on Thursday morning, you will need Saturdays’ full backup, and the incremental backups from Monday, Tuesday, and Wednesday to fully restore the system. Be sure you label the media appropriately, so you know which incremental backups go with which full backup. The advantages of a differential backup are: ✦ The backup takes less time to perform because not all files are being backed up. ✦ Fewer media are required because not as much data is being backed up. The disadvantages of this method are: ✦ Media must be restored in the correct order to bring the system back to its previous state. ✦ Backups are spread across multiple media. This can cause recovery to take longer. Differential backup Differential backups capture all the files that have changed since the last full backup. The archive bit is left on so the files will appear to the system as not having been backed up. This is different from incremental backups, because incremental 4809-3 ch19.F 5/15/01 9:50 AM Page 478 479 Chapter 19 ✦ Backing Up and Restoring backups include the files that have changed since the last full or incremental backup. Monday’s differential backup captures all the changes since the full backup on the weekend. Tuesday’s differential backup captures all the changes that occurred on Monday and Tuesday, and so on. If a file is changed on Monday, it will be backed up on both Monday and Tuesday, because the archive bit isn’t reset. Therefore, each differential backup replaces the previous one. This makes restoring easier, because you only need the most recent full backup, and the most recent dif- ferential backup. However, more data is backed up than with an incremental backup, which takes longer. The advantages of this method are: ✦ Restore the files requires only a full backup and the most recent differential. ✦ Restoring files is faster then with an incremental backup because only two backups are needed. This is a big advantage in disaster recovery. ✦ Files are easier to find because only two backups are required. The disadvantages of this method are: ✦ Backups are redundant because all the files that were created or modified since the last differential backup are included. ✦ Backups are more time consuming because differential backups done later in the week will take more time than incremental backups. Daily backup Daily backup can be performed in addition to the media rotation schedule that you are using. This method backs up all the files on your devices with today’s date. Essentially what this means is that a daily backup grabs all files that are created or changed today. The daily backup method does not reset the archive bit. Media Rotation Methods Another important factor in your backup plan is to determine how long each copy of a file needs to be kept. If you do not choose a media rotation method, each time the media becomes full, you have to archive it and purchase another one. Obviously, this is not practical in the sense that not all files need to be kept perma- nently, especially if they do not change regularly. The following sections discuss the most common methods for rotating your media. These methods are called son, father, and grandfather, because the “son” backup is the most recent. These meth- ods can be combined into more complex systems. 4809-3 ch19.F 5/15/01 9:50 AM Page 479 480 Part VII ✦ Disaster Recovery Son rotation method The son strategy involves doing a full backup every day, using the same media each time. This method typically only requires one tape (or other media). This is not the most effective method to implement even though it is easy to administer. Be cau- tious if you choose this strategy because the media you are using will eventually wear out after repeated use, and the data available only extends to your last backup. Figure 19-1 shows the backup rotation with the son method. Figure 19-1: Son rotation method Father-son rotation method The father-son media rotation method uses a combination of full and differential or incremental backups for a two-week schedule, as shown in Figure 19-2. There are four media used Monday through Thursday, for differential or incremen- tal backups. The Friday media contain full backups and are rotated out and usually stored off-site each week. This method requires six different tapes, and provides a two-week backup history. You are not limited to this scenario for a father-son strategy, although this is a very common one. For example, you could perform two full backups per week on Tuesday and Thursday, with incremental backups on Monday, Wednesday, and Friday. This scenario will definitely increase the security of the data, but it will take more time to do the full backups. Keeping three weeks of history would then require a minimum of eight tapes. Week 1 Monday Media 1 Tuesday Media 1 Wednesday Media 1 Full Backup Thursday Media 1 Friday Media 1 4809-3 ch19.F 5/15/01 9:50 AM Page 480 481 Chapter 19 ✦ Backing Up and Restoring Figure 19-2: Father-son rotation method Grandfather rotation method The grandfather method is one of the most popular media rotation methods, because it is fairly simple to administer, yet it is comprehensive enough to easily locate files for restoration. See Figure 19-3 for an example. There are four media used Monday through Thursday for differential and incremen- tal backups; these are reused every week. An additional three media are used every Friday for full backups; these are used only once a month, and are reused each month. Twelve additional media are used, one each month, for monthly full back- ups. These aren’t reused, and should be kept off-site. This strategy offers excellent storage life for the number of media used. Four daily tapes, three weekly tapes, and the twelve tapes for monthly backups are a total of nineteen tapes for one year. This way, your backup history extends for one full year. Week 1 Monday Media 1 Tuesday Media 2 Wednesday Media 3 Full Backup Incremental or Differential Backup Thursday Media 4 Friday Media 5 Week 2 Monday Media 1 Tuesday Media 2 Wednesday Media 3 Thursday Media 4 Friday Media 5 4809-3 ch19.F 5/15/01 9:50 AM Page 481 482 Part VII ✦ Disaster Recovery Figure 19-3: Grandfather rotation method Grandfather-father-son rotation method The grandfather-father-son method reduces the wear on the media, but the history is reduced to a 12-week period. In the Father-Son method, you will notice that the same four media are used over and over again in order to perform differential or incremental backups. The grandfather-father-son method eliminates this problem by rotating the media in such a way that allows all the media to be used equally over a 40-week period Figure 19-4 shows an example. The grandfather-father-son cycle begins with a full backup. After that, incremental or differential backups are performed Monday through Thursday. Each Friday, a full backup is performed, and the media are rotated, as in the grandfather method. On the fourth Friday of each month, a full backup is performed and should be stored off site. This method is divided into 10 four-week intervals. The same four media are used Monday through Thursday throughout the 12-week period, but are rotated at the start of the next quarter. Week 1 Monday Media 1 Tuesday Media 2 Wednesday Media 3 Thursday Media 4 Friday Media 5 Week 2 Monday Media 1 Full Backup Incremental or Differential Backup Tuesday Media 2 Wednesday Media 3 Thursday Media 4 Friday Media 6 Week 3 Monday Media 1 Tuesday Media 2 Wednesday Media 3 Thursday Media 4 Friday Media 7 Week 4 Monday Media 1 Tuesday Media 2 Wednesday Media 3 Thursday Media 4 Monthly 4809-3 ch19.F 5/15/01 9:50 AM Page 482 483 Chapter 19 ✦ Backing Up and Restoring Figure 19-4: Grandfather-Father-Son Media Rotation Method Week 1 Baseline Month 1 Month 2 Month 3 Monday Media 2 Tuesday Media 3 Wednesday Media 4 Thursday Media 5 Monday Media 2 Tuesday Media 3 Wednesday Media 4 Thursday Media 5 Monday Media 2 Tuesday Media 3 Wednesday Media 4 Thursday Media 5 Monday Media 2 Tuesday Media 3 Wednesday Media 4 Thursday Media 5 Monday Media 2 Tuesday Media 3 Wednesday Media 4 Thursday Media 5 Monday Media 2 Tuesday Media 3 Wednesday Media 4 Thursday Media 5 Monday Media 2 Tuesday Media 3 Wednesday Media 4 Thursday Media 5 Monday Media 2 Tuesday Media 3 Wednesday Media 4 Thursday Media 5 Monday Media 2 Tuesday Media 3 Wednesday Media 4 Thursday Media 5 Monday Media 2 Tuesday Media 3 Wednesday Media 4 Thursday Media 5 Monday Media 2 Tuesday Media 3 Wednesday Media 4 Thursday Media 5 Monday Media 2 Quarter 2 Daily media are 1-2-3-4 Weekly media are 5-6-7 Monthly media are 8-9-10 Quarter 3 Daily media are 11-1-2-3 Weekly media are 4-5-6 Monthly media are 7-8-9 Quarter 4 Daily media are 10-11-1-2 Weekly media are 3-4-5 Monthly media are 6-7-8 Tuesday Media 3 Wednesday Media 4 Thursday Media 5 Friday Media 1 Friday Media 6 Week 2 Friday Media 7 Week 3 Friday Media 8 Week 4 Friday Media 9 Week 5 Friday Media 6 Week 6 Friday Media 7 Week 7 Friday Media 8 Week 8 Friday Media 10 Week 9 Friday Media 6 Week 10 Friday Media 7 Week 11 Friday Media 8 Week 12 Friday Media 11 Differential or Incremental Backups Full Backups 4809-3 ch19.F 5/15/01 9:50 AM Page 483 484 Part VII ✦ Disaster Recovery You must: ✦ Perform a full backup on Media 10 when you start this strategy ✦ Start with media 2 on Monday Performing the above suggestions will ensure four-week old data at the end of the first four week cycle. Restoring data from a particular week or month using the grandfather-father-son method only requires one backup set. The advantages to this method are that all media are used equally, so the wear on the tapes is distributed, and it only requires 11 media, which is fewer than the grandfather method. However, keeping track of the rotation schedule makes this method more difficult to administer, and your backup history is only 12 weeks long. If you want to increase the number of months in your history, use more monthly tapes. Documenting Backup and Restoration Procedures 7.2 Restoring Preparing a backup and restoration plan is an integral part of accessing the com- pany’s protection level. The first step is to have documentation that lists the hard- ware and software environments. In short, you should keep track of the following items, although you are not limited to this list: ✦ Type of computer ✦ Add-on hardware (drives, printers, etc) ✦ Storage media ✦ Network connections ✦ Devices ✦ Model numbers ✦ Serial numbers ✦ Upgrade levels or service pack levels ✦ Software installed and its purpose Objective Exam Tip 4809-3 ch19.F 5/15/01 9:50 AM Page 484 485 Chapter 19 ✦ Backing Up and Restoring Many system administrators opt to purchase special software designed to automat- ically detect your hardware, software, and other devices, and it maintains them in a database. The big advantage to this is the reduced time it takes to catalog your environment and the ability to easily track new devices as they are added. However, this is not necessary as you can use a word processor or design you own database to perform the same task. The second step in the backup plan is to plan your off-site media rotation. This means having the proper software installed, and having the ability to know how to use these tools. This also means having your media transported off site by com- pany personal, or hiring a company that specializes in off-site tape storage. The big advantage to hiring a company is that they also keep detailed records of each tape that you give them, and each piece of media they return. You also do not have to worry about the employee being sick, or losing the tape. These companies should guarantee a high level of service, and have any number of employees to deliver the media upon your request. Hopefully, there is a reputable company that performs this service in your immediate area, because the closer they are, the less time you have to wait in the event of an emergency. Third, you should perform mock backup and restoration tests. Using the methods described in Chapter 17, you should use an off-site facility to accomplish this. Document everything that happens during the backup and restoration procedures, and the time it takes to accomplish each task. This includes the time it takes to install the operating system to the time it takes to restore all the necessary data. If you come across a problem during the backup, decide how will it affect your restoration. You will also need to ensure that you can restore the devices to their most recent states. This means that you will have to restore from the most recent full backup, and the subsequent incremental or differential backups based on the media rota- tion method you adopted. Make sure that you have correctly labeled all your media physically and electronically. For greater control and security, all backups should go off-site on a nightly basis. Disasters such as fires, flooding, earthquakes, tornadoes, and hurricanes, happen more often than one might expect. Don’t forget about your user workstations either, as some may have important files stored locally on their systems. Most backup soft- ware has agents that specialize in backing up and restoring workstations. You should treat this data with the same respect as your centralized server data. 4809-3 ch19.F 5/15/01 9:50 AM Page 485 [...]... because it offers the longest history for the number of media Depending on your situation, this is typically 19 media For more information, see the “Grandfather rotation method” section 493 48 09- 3 ch 19. F 494 5/15/01 9: 50 AM Page 494 Chapter 19 ✦ Study Guide 12 B You will need to purchase 19 media for a standard rotation strategy Four media will be used Monday through Thursday for the differential or... your house 48 09- 3 appA.F 5/15/01 9: 50 AM Page 495 A A P P E N D I X Exam Objective Mapping In this appendix, you’ll find the table listing the exam objectives for the Server+ certification exam The table is an exhaustive cross-reference chart that links every exam objective to the section in this book where the subject matter is covered ✦ ✦ ✦ ✦ 48 09- 3 appA.F 496 5/15/01 9: 50 AM Page 496 Appendixes... requested you increase it to three weeks of history that must be stored off-site How many tapes will need to be added in order to keep three weeks of history off-site? A 7 B 8 C 9 D 10 4 89 48 09- 3 ch 19. F 490 5/15/01 9: 50 AM Page 490 Chapter 19 ✦ Study Guide 11 The grandfather method is the most comprehensive media rotation method because: A The backup history extends to six months B The backup history extends... the computer systems back up and running in a short period of time What steps should you have taken regarding your backup plan? 491 48 09- 3 ch 19. F 492 5/15/01 9: 50 AM Page 492 Chapter 19 ✦ Study Guide Answers to Chapter Questions Chapter pre-test 1 Backing up data on your servers is perhaps the most important thing you can do as an administrator Backing up data will help to ensure that company’s data... storage agency, have copies at home in a fire safe, and keep copies in your desk 15 What is not a common type of backup media? A 4mm B 9mm C 8mm D DLT E DAT 48 09- 3 ch 19. F 5/15/01 9: 50 AM Page 491 Chapter 19 ✦ Study Guide 16 You have 30GB of data to backup from your database server You have a DAT backup system What tape format will you most likely be using? A DDS-1 B DDS-2 C DDS-3 D DDS-4 17 You are using... easier to find files D Backups are not redundant, thus time is not wasted backing up the same information later in the week 48 09- 3 ch 19. F 5/15/01 9: 50 AM Page 4 89 Chapter 19 ✦ Study Guide 7 What is the typical number of media used in the son rotation method? A 8 B 4 C 1 D 19 8 Why is the son strategy not the most effective one? Choose all that apply A It involves doing a full backup on weekends and... upgrade has been recognized; review and baseline; document the upgrade Performing an Upgrade Checklist 48 09- 3 appA.F 5/15/01 9: 50 AM Page 499 Appendix A ✦ Exam Objective Mapping Exam Objective Chapter Section Verify that server and OS recognize the added memory Chapter 7 Installing Memory Perform server optimization to make use of additional RAM Chapter 7 Installing Memory 3.5 Upgrade BIOS/firmware Chapter... connector D Battery-protected outlet 48 09- 3 appB.F 5/15/01 9: 50 AM Page 507 Appendix B ✦ Practice Exam 9 A company would like to connect 20 hard drives to their five database servers What is the best technology to use for this configuration? A Fast SCSI B UltraWide SCSI C UDMA D Fibre Channel 10 A technician is installing a new NIC into an existing server The server already has a serial mouse on COM... selected in the backup job The most common causes of this are usually the device being turned off, or being moved to a different location Answer A is incorrect because you would not 48 09- 3 ch 19. F 5/15/01 9: 50 AM Page 493 Chapter 19 ✦ Study Guide receive an error message if you forgot to schedule the job Answer C is incorrect because the software is most likely not wrong, and you should never ignore errors... upgrade hasbeen recognized; review and baseline; document the upgrade Chapter 7 Performing an Upgrade Checklist Continued 499 48 09- 3 appA.F 500 5/15/01 9: 50 AM Page 500 Appendixes Table A-1 (continued) Exam Objective Chapter Section 3.8 Upgrade system monitoring agents Chapter 9 Upgrading System Monitoring Tools Perform upgrade checklist including: locate and obtain latest test drivers, OS updates, . backup media? A. 4mm B. 9mm C. 8mm D. DLT E. DAT 490 Chapter 19 ✦ Study Guide 48 09- 3 ch 19. F 5/15/01 9: 50 AM Page 490 491 16. You have 30GB of data to backup from your database server. You have a DAT backup. is typically 19 media. For more information, see the “Grandfather rotation method” section. 493 Chapter 19 ✦ Study Guide 48 09- 3 ch 19. F 5/15/01 9: 50 AM Page 493 12. B. You will need to purchase 19 media. your house. 494 Chapter 19 ✦ Study Guide 48 09- 3 ch 19. F 5/15/01 9: 50 AM Page 494 A A APPENDIX Exam Objective Mapping In this appendix, you’ll find the table listing the exam objectives for the Server+ certification