After takin a swig o' Arrakan spice grog, martin@bugs.unl.edu.ar (Martin Marques) belched out:
> El Vie 02 Jul 2004 18:39, Jan Wieck escribió:
>> On 6/22/2004 11:51 PM, mike g wrote:
>> > Slony version 1 is supposed to be live very soon. You can test beta3 if
>> > you like.
>>
>> Slony-I version 1.0 is out now. It does not contain incremental backup.
>> This feature is on the TODO list for 1.1.
>
> I'm very interested in this.
> How is it that a replication system would give the ability of doing
> incremental backups?
The idea would be that you take a pg_dump at a point in time, which
provides, if you will, a "baseline."
You then take the series of logs containing Slony-I updates, which,
themselves, are a set of SQL Insert/Update/Delete statements. They
represent incremental updates.
The clever part was noticing that it would be useful to record those
updates in text form _as incremental SQL logs_.
> How would these incremental backups compare to Informix's level
> backups (level 0 is a full backup, 1 are the differences from the
> last 0, and 2 are the differences from the last level 1 BU)?
Well, supposing you take a pg_dump from a particular node starting at
time T; that's a "level 0" backup.
Slony-I then has a series of (say) 42 log files each dated after time
T, and going to time T + n. Together, they represent the "level 1"
differences between the "level 0" backup at time T and the present.
I suppose that the 42nd one might be considered to represent a "level
42" backup, as it depends on the preceding 41 logs as well as that
"level 0" backup.
It would be unsurprising for there to be hundreds, if not thousands of
such files per day...
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