| I think that data backup is a system administrator's | | | | always spin up or that you won't need to resort to a |
| most important function. You need to lose your data | | | | computer's humble diskette drive. Check yours now. |
| just once to convince you that I'm right. | | | | I'll bet that most diskette drives in older computers |
| Your backup medium (disk, tape, etc) must be | | | | no longer work . . . and good luck finding cleaning kits |
| (a) removable and | | | | for them! |
| (b) transportable. | | | | Why backing up files is necessary but not sufficient |
| When evaluating backup solutions, remember that | | | | Although up to date backups of your files are |
| speed of disaster recovery is most important, | | | | important, they're not sufficient to recover from a |
| followed by ease of following a backup routine. The | | | | server system disk crash. In order to use your |
| last factor that you should worry about is media | | | | backed-up files, they must be restored to a working |
| (tape, CD-R, disk) costs. | | | | server, and if the server won't run because its |
| You must routinely verify that the data can be read | | | | system disk has died, you're still out of luck. |
| from your backup media (tapes, DVDs, etc). Most | | | | A recovery from a server system disk crash includes |
| backup programs allow a tape verification to be | | | | re-installing the server operating system (Unix, |
| performed after each tape is written to. The | | | | NetWare, NT, etc) -- if you have the server |
| downside is that it almost doubles the duration of the | | | | operating system's install disks and license numbers. If |
| backup window and increases wear on the tape and | | | | not, you're out of luck. (You may also be out of |
| drive. Whether you verify each backup, or only | | | | business.) You'll also need software drivers for any |
| weekly backups, you must verify that your tapes | | | | special hardware and then you'll need to configure |
| can be read. | | | | them. |
| You'll need to decide whether your data is valuable | | | | A good alternative is to have a standby system disk |
| enough to encrypt its backups. The downside to | | | | ready that is a bit-by-bit image of your server's |
| encryption is that at restoration time, you must | | | | system disk. When (not if) the server's system disk |
| know the password. | | | | crashes, replace it with the standby system disk, |
| You must keep some backups off-site, to allow | | | | then restore your data files from the lastest backup |
| recovery in case your on-site tapes are stolen, | | | | set, and you're back in business. |
| crushed, flooded, or burnt to a crisp. | | | | Why redundant hardware isn't a substitute for a |
| I recommend that you maintain three generations of | | | | backup system |
| tapes: Grandfather, Father, Son. | | | | Maybe you think that because your programs and |
| The sons are written to each evening, the fathers | | | | data reside on redundant hardware such as RAID |
| are written to each week, and the grandfathers are | | | | that you don't need tape backup. Wrong. Redundant |
| written to each month. I recommend that you save | | | | hardware protects you from hardware failure, but |
| each month's backup. At the end of the year you'll | | | | does not protect you from software failure. |
| have twelve tapes -- one for each month of the | | | | Sometimes bad data, corrupted files, or program |
| year. (Try to restore a fraction of the data, just to | | | | faults don't appear for days or weeks until someone |
| ensure that the backup media is readable.) Store | | | | tries to access them. Your redundant hardware won't |
| these in a safe place, in case you ever need to | | | | help; you need to restore damaged files from a |
| restore old data. Besides, when disaster strikes, | | | | backup that predates the data corruption. No |
| Murphy's Law says that your first backup tape won't | | | | problem -- if you're following the grandfather - father |
| work when you try to restore from it. | | | | - son - tape rotation scheme. So bite the bullet and |
| Sometimes the monthly and weekly tapes contain full | | | | stock up on tapes now. |
| backups and the nightly tapes contain just | | | | Tape Libraries |
| incremental or differential backups. Keep in mind that | | | | Eventually, businesses outgrow hand-fed tape drives. |
| your goal is to recover from a disaster as quickly as | | | | The next step is tape libraries. (Visualize a jukebox |
| possible, so maybe it makes sense to backup | | | | that handles tape cartridges instead of records.) |
| everything every night. Your mileage may vary. | | | | They're pricey, require tape library software, and |
| Store your off-site tapes well away from your site. | | | | take time to configure, but once in production with |
| Many small businesses give their monthly backups to | | | | the right software, they handle the nightly backup |
| a manager to keep at home. Larger businesses | | | | chores unattended. Perhaps once a week or once a |
| contract with services that transport their off-site | | | | month, someone must attend to the library for an |
| tapes to secure storage facilities. | | | | hour or so, to remove archival tapes and feed it |
| As you put together a disaster recovery plan, plan | | | | fresh meat . . . er, tapes. |
| on the worst-case. Don't assume that disks will | | | | What's my favorite tape medium? DLT. By a mile. |