View Full Version : Question about Amanda backup strategy

September 3rd, 2010, 07:18 AM
Hello Everyone,

I have the configuration defined as following.

dumpcycle 7 # the number of days in the normal dump cycle
runspercycle 7 # the number of amdump runs in dumpcycle days
# (4 weeks * 5 amdump runs per week -- just weekdays)
tapecycle 2

runtapes 1

Basically what I want to do is do a full backup once a week and incremental on the rest of the week. I have scheduled the backups every morning around 1 am.

I am only using two tapes. When it does incrementals does it append to a used tape (knowing that the tape still has space left) or does it always want a new tape?

Charles Curley
September 6th, 2010, 11:11 AM
It always wants a new tape.

The rational is that if something ate a blank tape or one with old data on it, that would be no great loss. If it eats a tape with last night's back up, you are in trouble.

Because Amanda schedules total backups itself, you should have enough tapes to have twice the number you need per dump cycle, plus some spares. So if your dumpcycle is 7 and you use 7 tapes per cycle, you should have at least 15, maybe 17 tapes.

You can approximate appending by delaying writes to tape (http://wiki.zmanda.com/index.php/How_To:Delay_writing_to_tape_for_better_tape_utili zation), but that has its own reliability/failure issues.

September 9th, 2010, 12:59 PM
I know that the dump-cycles runspercycle tapespercycle also guides amanda regarding retention policy.

Is there directive in amanda.conf that configures a retention-policy. There is a link but I am not sure if its referring to amanda.

Charles Curley
September 10th, 2010, 06:12 AM
I think not. I see no reference to retention-policy in the man page for amanda.conf (http://wiki.zmanda.com/man/amanda.conf.5.html).