Background
We're designing the architecture of a new system using Elasticsearch now, and we plan to use Elastic Cloud based on reviews contrasting their service with AWS's, and self-hosting on an EC2 instance. As we design the system, I'm trying to learn from a small test project my team deployed on Elastic Cloud 6 months ago. While I've spent a lot of time reading the Elasticsearch Docs, Elasticsearch: The Definitive Guide, and Elastic Cloud's Docs, there are some concepts here that I'm still not understanding.
Our Test Project's issues
Our test project uses the default of 5 primary shards and 1 replica shard per primary. It was configured using the default deployment options on Elastic Cloud with a single one node, currently with 2GB of memory. Because there is only one node, and because replica shards are never assigned to the same node as their primary shard (reason 2), none of the replicas are getting assigned. Also, this project uses time-based data, and is creating one index per account per day, resulting in about 10 indexes per day (or 100 shards), and over time, the proverbial Kagillion Shards. This system was only ever meant to have several months of data on it at a time, so the solution has been to manually delete old data when memory on this deployment runs out.
The New System
Our new system is meant to have 5 years worth of time based-data on it, which is projected to grow to 250 GB in size. The current implementation uses a single index for the time-based data, with 6 primary shards and 1 replica per primary. This decision was made based on reading that a single shard should aim for a maximum of 30GB in size.
Questions
- Our old system had one node with too many indexes (over 100) and too many shards (over 1000), and it seems like our new one is being designed with too few (one index for 5+ years of data). It seems a better indexing strategy according to the time-based data recommendations would be to create one index per week or month? That being said, according to another answer on SO the optimal number of indexes per node is 1, so what is the utility in creating multiple indices for time-based data in the first place if we're only running on one node?
- How does one add a node to an ES deployment in Elastic Cloud? Currently all of the replica nodes in the test project are unassigned, because the deployment only has one node. There is a slider which allows you to easily choose the memory of each node in a deployment (between 1GB and 250B), however I see no way to add multiple nodes, which is confusing because it seems like basic functionality for Elasticsearch.
- Our test project's node has restarted several times, always when there is lots of old data on the node, and therefore memory pressure. The solution has been to delete old data (as the test project was only meant to have several months of data at a time), but it appears the node didn't lose data when it restarted. Why would this be?
- Our test project has taken no snapshots, which are supposed to happen automatically on Elastic Cloud every 30 minutes. I've asked their support about this, but just curious to see if anyone knows what could cause this and how to resolve it?