Friday night, a dead disk
The file server at Hartley Print Shop fails on Friday night. Eight years of customer orders are on it.
On Monday the owner asks: "Did anyone take a backup? Can we get it back?" Today you learn the regular jobs that make the answer yes.
By the end of this lesson
Note
I can plan the regular maintenance jobs for a small business and say how often each is done.
Key words
| Word | What it means |
|---|---|
| Backup | a copy of data kept so it can be restored |
| Restore | to put backed-up data back in place |
| Full backup | a copy of everything |
| Incremental backup | a copy of what changed since the last backup of any kind |
| Differential backup | a copy of what changed since the last full backup |
| Work log | a dated record of the jobs a manager has done |
| Network | devices joined so they can share data |
| Malware | software made to cause harm |
The cells students fill in are left blank in this preview.
Starter: what you already know
Have a go
Starter: what you already know
3 questionsYour answers are marked here and are not kept. A college account keeps every student’s marks.
Three ways to take a backup
A full backup copies everything. It is slow, but a restore needs only that one copy.
An incremental backup copies only what changed since the last backup of any kind. It is quick, but a restore needs the full copy and every increment after it.
A differential backup copies what changed since the last full backup. It grows each day, but a restore needs only two copies.
Worked example: a week of backups
| Day | Incremental plan | Differential plan | Files copied that day |
|---|---|---|---|
| Sunday | Full | Full | All files |
| Monday | Changes since Sunday | Changes since Sunday | Monday's changes |
| Tuesday | Changes since Monday | Changes since Sunday | Incremental: Tuesday only. Differential: Monday and Tuesday |
| Wednesday | Changes since Tuesday | Changes since Sunday | Incremental: Wednesday only. Differential: Monday to Wednesday |
The cells students fill in are left blank in this preview.
What a restore on Wednesday night needs
| Plan | Copies needed | Speed to take | Speed to restore |
|---|---|---|---|
| Full every day | The latest full copy | Slowest | Fastest |
| Full plus incremental | Sunday full, plus Monday, Tuesday and Wednesday | Fast | Slower, and one lost copy breaks the chain |
| Full plus differential | Sunday full, plus Wednesday | Medium | Medium |
The cells students fill in are left blank in this preview.
Check
Have a go
Check
4 questionsYour answers are marked here and are not kept. A college account keeps every student’s marks.