> Maybe I'm missing something, but AFAIK plain old RAID will not protect
> you against any scenario except failure of a single disk. It certainly
> won't do anything to help you revert to a prior database state.
> won't do anything to help you revert to a prior database state.
The idea for RAID came from https://www.postgresql.org/docs/current/different-replication-solutions.html
A modified version of shared hardware functionality is file system replication, where all changes to a file system are mirrored to a file system residing on another computer. The only restriction is that the mirroring must be done in a way that ensures the standby server has a consistent copy of the file system — specifically, writes to the standby must be done in the same order as those on the primary. DRBD is a popular file system replication solution for Linux.
DRBD seems to work similar to RAID but over network, but I might be wrong.
According to that link (https://www.postgresql.org/docs/current/backup-file.html):
> An alternative file-system backup approach is to make a “consistent snapshot” of the data directory, if the file system supports that functionality (and you are willing to trust that it is implemented correctly).
> The typical procedure is to make a “frozen snapshot” of the volume containing the database
1. Periodic snapshots using EBS mechanism (to get consistent snapshots).
2. Periodic pg_basebackup + WAL file archiving ( to allow reverting to a previous step if we e.g. mistakenly drop a table).
Thanks,
Tom
On Thu, Dec 30, 2021 at 12:52 PM Tom Lane <tgl@xxxxxxxxxxxxx> wrote:
Tom Korach <tom@xxxxxxxxxxxx> writes:
>> What do you mean exactly by "file-system replication"?
> RAID1 setup (specifically, between two disks or EBS volumes [on AWS]),
> using LVM.
Maybe I'm missing something, but AFAIK plain old RAID will not protect
you against any scenario except failure of a single disk. It certainly
won't do anything to help you revert to a prior database state.
The docs page I pointed you to is part of a chapter that lays out all
the backup methods the PG community considers reliable. I strongly
suggest sticking to one of those and not trying to take shortcuts.
(The following chapter on high-availability setups is relevant
reading as well.)
regards, tom lane
