dumpcycle & runspercycle

[Nox]

I'm trying to fully understand the dumpcycle and runspercycle settings in amanda.conf. Taken from the wiki:

Dumpcycle
From The Open Source Backup Wiki (Amanda, MySQL Backup)

The dumpcycle tells Amanda when to do a full dump in conjunction with the runspercycle parameter. The dumpcycle represents the number of days over which every filesystem will have a full backup. If I want a complete backup of every system every night then my dumpcycle would be 0. Every 7 days would get me a full backup each week.

Runspercycle indicates how many time in the above dumpcycle that the amdump program will be executed. If you do a backup every weekday night but wanted a full backup each week then your dumpcycle would be 7 and and your runspercycle would be 5.

Please see amanda.conf(5) for information on amanda.conf parameters.

The part that confuses me is the dumpcycle = 7 and the runspercycle = 5.

If my dumpcycle is 7 and my runspercycle is 5, then amdump, which is the program that performs the backups, will only run 5 times within a given cycle? So the 6th and 7th day, nothing happens, even if cron tells the backup to run, correct?


So why can't you simply have dumpcycle = 5 and runs per cycle = 5 and just have cron control the times when the backup runs? Essentially if your backup always starts with a full backup, and the next 4 runs after that are incremental, and provided you have 10 tapes in rotation, you have 2 weeks of daily backups before your media is reused.

Why would you ever set the dumpcycle to 7 and the runspercycle to only 5?

[martineau]

So why can't you simply have dumpcycle = 5 and runs per cycle = 5 and just have cron control the times when the backup runs?

Amanda will perform a full dump every 5 days (73 times a year)

Essentially if your backup always starts with a full backup, and the next 4 runs after that are incremental, and provided you have 10 tapes in rotation, you have 2 weeks of daily backups before your media is reused.

Why would you ever set the dumpcycle to 7 and the runspercycle to only 5?

It is what most people want, a full dump every 7 days (52 times a year)

And you must set your cron to run amdump only 5 time in 7 days

[pyeatman]

Amanda will perform a full dump every 5 days (73 times a year)


It is what most people want, a full dump every 7 days (52 times a year)

And you must set your cron to run amdump only 5 time in 7 days

I'll add to this that I think you are believing that by specifying runspercycle, you are requesting of Amanda to perform that number of dumps per dumpcylce. As it is you who always initiates an amdump (not Amanda), you are actually simply informing Amanda of how many dumps you are planning on doing within the given dumpcycle period so that Amanda knows what to anticpate and thus plans things accordingly.

Paul