From 871c2c13dd34189ab54e1fbdc485959cf05c8cfd Mon Sep 17 00:00:00 2001 From: Sebastian Bernauer Date: Thu, 21 Sep 2023 15:25:21 +0200 Subject: [PATCH] wording --- .../hdfs/pages/usage-guide/operations/pod_disruptions.adoc | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-) diff --git a/docs/modules/hdfs/pages/usage-guide/operations/pod_disruptions.adoc b/docs/modules/hdfs/pages/usage-guide/operations/pod_disruptions.adoc index 51416af2..8e1700d0 100644 --- a/docs/modules/hdfs/pages/usage-guide/operations/pod_disruptions.adoc +++ b/docs/modules/hdfs/pages/usage-guide/operations/pod_disruptions.adoc @@ -15,12 +15,12 @@ We only allow a single namenode to be offline at a given time, regardless of the For datanodes the questions how many instances can be offline at the same time is a bit harder: HDFS stores your blocks on the datanodes. Every block can be replicated multiple times (to multiple datanodes) to ensure maximum availability. -The default setting is a replication of `3` - which can be configured using `spec.clusterConfig.dfsReplication`. However, it is also possible to change the replication factor for a specific file or directory to something else than the cluster default. +The default setting is a replication factor of `3` - which can be configured using `spec.clusterConfig.dfsReplication`. However, it is also possible to change the replication factor for a specific file or directory to something else than the cluster default. -When you have a replication of `3`, you can safely can take down 2 datanodes, as there will always be a third one holding the blocks of the two down datanodes. +When you have a replication of `3`, you can safely can take down 2 datanodes, as there will always be a third datanode one holding a copy of the block on the two unavailable datanodes. However, you need to be aware that you are now down to a single point of failure - the last of the three replicas! -Taking this into consideration, our operator uses the following algorithm to determine the maximum number of datanodes allowed to be offline. +Taking this into consideration, our operator uses the following algorithm to determine the maximum number of datanodes allowed to be offline: `num_datanodes` is the number of datanodes in the HDFS cluster, summed over all roleGroups. `dfs_replication` is default replication factor of the cluster.