Apache Mesos is a cluster manager that provides efficient resource isolation and sharing across distributed applications, or frameworks. It can run Hadoop, MPI, Hypertable, Spark, and other frameworks on a dynamically shared pool of nodes.
Apache Helix is a generic cluster management framework used for the automatic management of partitioned, replicated and distributed resources hosted on a cluster of nodes. Helix automates reassignment of resources in the face of node failure and recovery, cluster expansion, and reconfiguration.
Both are cluster managers, which one to choose and why?
Here is what I wrote on Apache Helix vs YARN which is applicable to Mesos v/s Helix. YARN/Mesos and Helix are complementary to each other.
You use Helix to build your system and manage the internal state of your system. Once the system is built it can be either deployed independently or deployed using YARN/Mesos.
@janisz, Helix is widely used and actively developed.