Re: Portworx snapshots

Greetings,

* Ghislain ROUVIGNAC (ghr@sylob.com) wrote:
> Portworx says that on a running PostgreSQL it can:
>
>    - replicate volumes for failover
>    - take snapshots of volumes
>    - backup volumes

The downside with any snapshot-style approach is that it means that when
you have a failure, you have to go through and replay all the WAL since
the last checkpoint, which is single-threaded and can take a large
amount of time.

This is why PostgreSQL has streaming replication, where we are
constantly sending WAL to the replica and replaying it immediately, and
that also allows us to have synchronous replication that is quorum based
and works with PostgreSQL, unlike what a snapshot level system would
provide.

When doing your testing, I'd strongly recommend that you have a large
max_wal_size, run a large pgbench which writes a lot of data, and see
how long a failover takes with this system.

> Does someone use them in production ?
> How reliable are these features ?
> Are there performance impacts of snapshots ?

I don't know anything about the actual utilization of this in production
or if this implementation is reliable, just to be clear.  My comments
specifically are about the performance of using a snapshot-based
approach (which could be this solution or various other ones).

Thanks!

Stephen