Tape Requirements for the Daily Cumulative, Weekly Incremental Backup Schedule

With this schedule, you need six tapes (if you want to reuse daily tapes), or nine tapes (if you want to use four different daily tapes): one tape for the level 0, four tapes for Fridays, and one or four daily tapes.

If you need to restore a complete file system, you need the following tapes: the level 0, all the Friday tapes, and the most recent daily tape since the last Friday tape (if any).

Example--Daily Incremental, Weekly Cumulative Backups

The following table shows a schedule where each weekday tape contains only the files that changed since the previous day, and each Friday's tape contains all files changed since the initial level 0 at the beginning of the month.

Table 45-10 Daily Incremental/Weekly Cumulative Backup Schedule

	Floating	Mon	Tues	Wed	Thurs	Fri
1st of Month	0
Week 1		3	4	5	6	2
Week 2		3	4	5	6	2
Week 3		3	4	5	6	2
Week 4		3	4	5	6	2

The following table shows how the contents of the tapes can change across two weeks with the daily incremental, weekly cumulative schedule. Each letter represents a different file.

Table 45-11 Contents of Tapes for Daily Incremental/Weekly Cumulative Backup Schedule

	Mon	Tues	Wed	Thurs	Fri
Week 1	a b	c d	e f g	hi	a b c d e f g h i
Week 2	j k l	m	n o	p q	a b c d e f g h i j k l m n o p q r s

Tape Requirements for Daily Incremental/Weekly Cumulative Schedule

With this schedule, you need at least nine tapes (if you want to reuse daily tapes--not recommended), or 21 tapes (if you save weekly tapes for a month): one tape for the level 0, four tapes for the Fridays, and four or 16 daily tapes.

If you need to restore the complete file system, you need the following tapes: the level 0, the most recent Friday tape, and all the daily tapes since the last Friday tape (if any).

Example--Monthly Backup Schedule for a Server

The following table shows an example backup strategy for a heavily used file server on a small network where users are doing file-intensive work, such as program development or document production. This example assumes that the backup period begins on a Sunday and consists of four seven-day weeks.

Table 45-12 Example of Monthly Backup Schedule for a Server

Directory	Date	Level	Tape Name
root (/)	1st Sunday	0	n tapes
/usr	1st Sunday	0	n tapes
/export	1st Sunday	0	n tapes
/export/home	1st Sunday	0	n tapes
	1st Monday	9	A
	1st Tuesday	9	B
	1st Wednesday	5	C
	1st Thursday	9	D
	1st Friday	9	E
	1st Saturday	5	F
root (/)	2nd Sunday	0	n tapes
/usr	2nd Sunday	0	"
/export	2nd Sunday	0	"
/export/home	2nd Sunday	0	"
	2nd Monday	9	G
	2nd Tuesday	9	H
	2nd Wednesday	5	I
	2nd Thursday	9	J
	2nd Friday	9	K
	2nd Saturday	5	L
root (/)	3rd Sunday	0	n tapes
/usr	3rd Sunday	0	"
/export	3rd Sunday	0	"
/export/home	3rd Sunday	0	"
	3rd Monday	9	M
	3rd Tuesday	9	N
	3rd Wednesday	5	O
	3rd Thursday	9	P
	3rd Friday	9	Q
	3rd Saturday	5	R
root (/)	4th Sunday	0	n tapes
/usr	4th Sunday	0	"
/export	4th Sunday	0	"
/export/home	4th Sunday	0	"
	4th Monday	9	S
	4th Tuesday	9	T
	4th Wednesday	5	U
	4th Thursday	9	V
	4th Friday	9	W
	4th Saturday	5	X

With this schedule, you use 4n tapes (the number of tapes needed for four full backups of the root (/), /usr, /export, and /export/home file systems), plus 24 additional tapes for the incremental backups of the /export/home file systems. This schedule assumes that each incremental backup uses one tape and that you save the tapes for a month.

Here's how this schedule works:

1. On each Sunday, do a full backup (level 0) of the root (/), /usr, /export, and /export/home file systems. Save the level 0 tapes for at least 3 months.

2. On the first Monday of the month, use tape A to do a level 9 backup of the /export/home file system. The ufsdump command copies all files changed since the previous lower-level backup (in this case, the level 0 backup that you did on Sunday).

3. On the first Tuesday of the month, use tape B to do a level 9 backup of the /export/home file system. Again, the ufsdump command copies all files changed since the last lower-level backup, which is Sunday's level 0 backup.

4. On the first Wednesday, use tape C to do a level 5 backup. The ufsdump command copies all files that changed since Sunday.

5. Do the Thursday and Friday level 9 backups on tapes D and E. The ufsdump command copies all files that changed since the last lower-level backup, which is Wednesday's level 5 backup.

6. On the first Saturday of the month, do a level 5 backup of /export/home, which copies all files changed since the previous lower-level backup (in this case, the level 0 backup you did on Sunday). Store tapes A-F until the first Monday of the next 4-week period, when you use them again.

7. Repeat steps 1-6 for the next three weeks, using tapes G-L and 4n tapes for the level 0 on Sunday, and so on.

8. For each 4-week period, repeat steps 1-7, using a new set of tapes for the level 0s and reusing tapes A-X for the incremental backups. The level 0 tapes could be reused after 3 months.

   This schedule lets you save files in their various states for a month. This plan requires many tapes, but ensures that you have a library of tapes to draw upon. To reduce the number of tapes, you could reuse Tapes A-F each week.

Suggestions for Scheduling Backups

The following table provides other suggestions for scheduling backups.

Table 45-13 Suggestions for Backup Schedules

File Restoration Need	Backup Interval	Comments
To restore different versions of files (for example, file systems that are used for word processing)	Do daily incremental backups every working day. Do not reuse the same tape for daily incremental backups.	This schedule saves all files modified that day, as well as those files still on disk that were modified since the last backup of a lower level. However, with this schedule, you should use a different tape each day because a file that changed on Tuesday, and again on Thursday, goes onto Friday's lower-level backup looking like it did Thursday night--not Tuesday night. If a user needs the Tuesday version, you cannot restore it unless you have a Tuesday backup tape (or a Wednesday backup tape). Similarly, a file that is present on Tuesday and Wednesday, but removed on Thursday, does not appear on the Friday lower-level backup.
To quickly restore a complete file system	Do lower-level backups more frequently.	--
To backup a number of file systems on the same server	Consider offsetting the schedule for different file systems.	This way you're not doing all level 0 backups on the same day.
To minimize tapes	Increase the level of incremental backups that are done across the week.	Only changes from day to day are saved on each daily tape.
	Increase the level of backups that are done at the end of the week. Put each day's and week's incremental backups onto the same tape.	Only changes from week to week (rather than the entire month) are saved on the weekly tapes.
	Put each day's and week's incremental backups onto the same tape.	To do so, use the no rewind option in the ufsdump command.