One question that surfaces regularly in the Percona forums: Does every node in a Percona XtraDB Cluster (PXC) need to have XtraBackup installed? It's a fair question, especially when managing a mixed environment or trying to minimize the software footprint on certain nodes. Here is what the actual mechanics and testing confirm.

The Short Answer (But Read On)

It depends on what you want that node to do. The nuance matters quite a bit here, so it is worth walking through how State Snapshot Transfer (SST) works in PXC and why XtraBackup's presence — or absence — on a given node is significant.

A Quick Refresher on SST in PXC

When a new node joins a Percona XtraDB Cluster, or when an existing node has been down long enough that Incremental State Transfer (IST) is no longer possible, the cluster performs a State Snapshot Transfer (SST). This is essentially a full data …

When using the Percona Operator for MySQL based on Percona XtraDB Cluster (PXC), it’s common to encounter scenarios where cluster nodes request a full State Snapshot Transfer (SST) when rejoining the cluster. One typical scenario where a State Snapshot Transfer (SST) is required is when a node has been offline long enough that the GCache […]

Even though I used a dedicated Kubernetes cluster to host my test database, I had this belief that by not explicitly allocating (or requesting, in Kubernetes vocabulary) CPU resources to my Percona XtraDB Cluster (PXC) pods or yet making just a small request, Kubernetes could be delaying access to the free CPU cycles available on […]

If you were to ask me the question, “Would it be possible to set up a replicate filter within the Percona XtraDB Cluster?” my immediate response would be to question you right back. Why would you even want the cluster nodes to have different data when you’re using a synchronous replication cluster? That’s because, instinctively, […]

When we run a SELECT in a replica server and it returns a different result to the one we would have obtained had we queried the source server instead, due to changes in the dataset that have not yet been replicated or synchronized to the replica, we get what is known as a stale read. My colleague Marcelo has blogged about Stale Reads and How to Fix Them before.

The need to avoid stale reads is a constraint that leads people into migrating to Percona XtraDB Cluster (PXC) / Galera Cluster or, more recently, Group Replication. I am focusing on PXC and Galera in this short blog post, which, similar to Group Replication, implements not exactly a synchronous replication model but what is commonly referred to as a …

In April 2021, I wrote an article about Online DDL and Group Replication. At that time we were dealing with MySQL 8.0.23 and also opened a bug report which did not have the right answer to the case presented. 

Anyhow, in that article I have shown how an online DDL was de facto locking the whole cluster for a very long time even when using the consistency level set to EVENTUAL.

This article is to give justice to the work done by the MySQL/Oracle engineers to correct that annoying inconvenience. 

Before going ahead, let us remember how an Online DDL was propagated in a group replication cluster, and identify the differences with what happens now, all with the consistency level set to EVENTUAL ( …

Multi-writer replication has been a challenge in the MySQL ecosystem for years before truly dedicated solutions were introduced – first Galera (and so Percona XtradDB Cluster (PXC)) replication (around 2011), and then Group Replication (first GA in 2016).

Now, with both multi-writer technologies available, do we still need traditional asynchronous replication, set up in active-active topology? Apparently yes, there are still valid use cases. And you may need it not only when for some reason Galera/PXC or GR are not suitable, but also when you actually use them. Of course, the most typical case is to have a second cluster in a different …

Apologies for the silly title, but the issue is a real one, even though it is not a new thing. Schema upgrades are not an ordinary operation in Galera. For the subject at hand, the bottom line is: under the default Total Order Isolation (TOI) method, “the cluster replicates the schema change query as a statement before its execution.” What this means in practice is that a DDL issued in one node is replicated to other nodes in the cluster before it is even executed in the source node, let alone completed successfully.

As a result of this, it may fail in one node and be successful in another, and this without raising loud alerts or stopping nodes to protect against data inconsistency. This is not a bug in itself but rather a compromise of design. With new changes in MySQL and the …

It is no secret that compute and storage costs are the main drivers of cloud bills. Migration of data from the legacy data center to the cloud looks appealing at first as it significantly reduces capital expense (CapEx) and keeps operational expenses (OpEx) under control. But once you see the bill, the lift and shift project does not look that promising anymore. See Percona’s recent open source survey which shows that many organizations saw an unexpected growth around cloud and data.

Storage growth is an organic process for the expanding business: more customers store more data, and more data needs more backups and disaster recovery storage for low RTO.

Today, the Percona Innovation Team, which is part of the Engineering organization, is proud to announce a new feature – High Compression. With this feature enabled, …

In Percona Kubernetes Operator for Percona XtraDB Cluster (PXC) versions prior to 1.5.0, there were two methods for upgrading PXC clusters, and both of these use built-in StatefulSet update strategies. The first one is manual (OnDelete update strategy) and the second one is semi-automatic (RollingUpdate strategy). Since the Kubernetes operator is about automating the database management, and there are use cases to always keep the database up to date, a new smart update strategy was implemented.

Smart Update Strategy

The smart update strategy can be used to enable automatic context-aware upgrades of PXC clusters between minor versions. One of the use cases for automatic upgrades is if you want to get security …