Steffen Heil (Mailinglisten) skriver:

>
> Hi
>
> > > I could simply create backups with incrementing levels, move the
> > > backup to the other server(s) and apply them there (that database is
> > > offline).
> > > However, I suspect there is a limit for the number of backup levels a
> > > database can have.
>
> > You don't need a lot of backup levels to do what you want. For
> example, Do a level 0 backup once a month/year/whatever, then do a
> > level 1 backup every weekend, a level 2 backup every day, and if
> required a level 3 backup every hour/whatever.
>
> For another type of service I already have a backup script that
> creates 5 levels of backups:
> Level 0 at the first Sunday of every quarter.
> Level 1 at the first Sunday every month.
> Level 2 at every Sunday.
> Level 3 every day.
> Level 4 every hour.
>
> But for this project I want more than hourly consistency. I am
> targeting 5 minuites or even less. That could be done using:
> Level 5 every 5 minutes.
>
> However in this case there might be lots of days with nearly no
> difference and then there may be some days with gigabytes of changes.
> Using an approach as above would mean to copy all these changes up to
> 23 times...
> I would really like to prevent that kind of extra traffic AND more
> important that delay in synchronization.
> Moreover, the servers hard drives may be rather slow and the database
> may grow up to 200 GB.
> (During operation there are relatively few reads and only some writes,
> the database is idle 99% of the time, so for operation the slow
> io system is not a problem.)
>

I understand your problem. Would it be possible to measure the size of
each level 5 backup, and if it's over a certain threshold use a higher
level for the rest of that day to keep from copying the same large set
of data over and over?

In essence, you would create a script that backs up every five minutes,
and if the last backup size was below a certains threshold use the same
level as before, otherwise bump it up. Reset to level 3 each night.

The benefit is that you won't create a large number of levels unless
it's actually needed to reduce backup traffic.

Regards,
Kjell