On Mon, Oct 21, 2019 at 4:19 PM Fabio Ugo Venchiarutti <f.venchiarutti@xxxxxxxxx> wrote:
On 21/10/2019 09:52, Luca Ferrari wrote:
> On Sat, Oct 19, 2019 at 7:46 PM Daulat Ram <Daulat.Ram@xxxxxxxxxxxxxxx> wrote:
>> One more questions is, how backups are useful if we have streaming replication . As I know, we can promote the standby as primary in case of disaster at primary side. Do we need to schedule backups if we have streaming replication?
>
> Let's speculate a little on that: do you need backups if you have a
> RAID-1 configuration?
> Replication helps you reduce almost to zero the time to handle a
> disaster, backups allow you to recover in a more large time window.
>
> Luca
>
>
TBH I hear this argument more often than I wish.
Offline backups and data replication are nearly entirely orthogonal.
Any form of instantaneous redundancy (RAID, instantaneous replication
and so on) primary is a mitigation measure to protect data &
availability against loss of infrastructure.
Backups (preferably with PITR) also do that, but that's not their
primary purpose unless you can't afford live redundancy on top of them.
Offline backups address many failure scenarios that any form of live
replication is defenseless against (eg: logical damage to the data as a
result of human errors/bugs/vandalism would hit all your replicas, but
you always can perform DR from a backup).
I think we are way ahead of the days where we need to live on Offline backups involving downtimes.
Today, we have several Online Consistent Backup solutions such as pg_basebackup (built-in with PG), pgBackRest, BARMAN, WAL-G etc ....
Online Consistent Backups + Archiving of WALs are perfectly reliable.
Online Consistent Backups + Archiving of WALs are perfectly reliable.
We need to ensure that we have safe backup locations, for example, push them to AWS S3 and forget about redundancy.
Why do you think only Offline Backups are reliable today ?
Delayed replicas, or any online rollback capability (such as pg_rewind
off the server's own pg_wal or Oracle's flashback), somewhat live in a
grey area in between, and their effectiveness varies depending on which
level was compromised.
What if you delay your replica by a day, before you making a change tomorrow (that may need a rollback). Delayed Replica is for emergencies IMO and of course does not satisfy every possible scenario.
--
Regards
Fabio Ugo Venchiarutti
OSPCFC Network Engineering Dpt.
Ocado Technology
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Thanks,
Avinash Vallarapu.
Avinash Vallarapu.
