[DOCS] Rewrite of sizing your shards-rebase (#124444)

* Edits copied over from #120346

* Update docs/reference/how-to/size-your-shards.asciidoc

Co-authored-by: shainaraskas <[email protected]>

* Improve Scanability

Co-authored-by: shainaraskas <[email protected]>

* Reduced what is a shard section for concision

* Adjusted title

* Add general and distribution sizing guidelines.

---------

Co-authored-by: shainaraskas <[email protected]>
Co-authored-by: George Wallace <[email protected]>

Author: 3 people

docs/reference/how-to/size-your-shards.asciidoc

@@ -1,17 +1,40 @@
 [[size-your-shards]]
 == Size your shards
+[discrete]
+[[what-is-a-shard]]
+=== What is a shard?
+
+A shard is a basic unit of storage in {es}. Every index is divided into one or more shards to help distribute data and workload across nodes in a cluster. This division allows {es} to handle large datasets and perform operations like searches and indexing efficiently. For more detailed information on shards, see <<nodes-shards, this page>>.
+
+[discrete]
+[[sizing-shard-guidelines]]
+=== General guidelines
+
+Balancing the number and size of your shards is important for the performance and stability of an {es} cluster:
+
+* Too many shards can degrade search performance and make the cluster unstable. This is referred to as _oversharding_.
+* Very large shards can slow down search operations and prolong recovery times after failures.
+
+To avoid either of these states, implement the following guidelines:
+
+[discrete]
+[[general-sizing-guidelines]]
+==== General sizing guidelines
+
+* Aim for shard sizes between 10GB and 50GB
+* Keep the number of documents on each shard below 200 million
+
+[discrete]
+[[shard-distribution-guidelines]]
+==== Shard distribution guidelines
 
-Each index in {es} is divided into one or more shards, each of which may be
-replicated across multiple nodes to protect against hardware failures. If you
-are using <<data-streams>> then each data stream is backed by a sequence of
-indices. There is a limit to the amount of data you can store on a single node
-so you can increase the capacity of your cluster by adding nodes and increasing
-the number of indices and shards to match. However, each index and shard has
-some overhead and if you divide your data across too many shards then the
-overhead can become overwhelming. A cluster with too many indices or shards is
-said to suffer from _oversharding_. An oversharded cluster will be less
-efficient at responding to searches and in extreme cases it may even become
-unstable.
+To ensure that each node is working optimally, distribute shards evenly across nodes. Uneven distribution can cause some nodes to work harder than others, leading to performance degradation and instability. 
+
+While {es} automatically balances shards, you need to configure indices with an appropriate number of shards and replicas to allow for even distribution across nodes.
+
+If you are using <<data-streams>>, each data stream is backed by a sequence of indices, each index potentially having multiple shards. 
+
+In addition to these these general guidelines, you should develop a tailored <<create-a-sharding-strategy, sharding strategy>> that considers your specific infrastructure, use case, and performance expectations. 
 
 [discrete]
 [[create-a-sharding-strategy]]
@@ -208,6 +231,7 @@ index can be <<indices-delete-index,removed>>. You may then consider setting
 <<indices-add-alias,Create Alias>> against the destination index for the source 
 index's name to point to it for continuity. 
 
+See this https://www.youtube.com/watch?v=sHyNYnwbYro[fixing shard sizes video] for an example troubleshooting walkthrough.
 
 [discrete]
 [[shard-count-recommendation]]
@@ -571,6 +595,8 @@ PUT _cluster/settings
 }
 ----
 
+See this https://www.youtube.com/watch?v=tZKbDegt4-M[fixing "max shards open" video] for an example troubleshooting walkthrough. For more information, see <<troubleshooting-shards-capacity-issues,Troubleshooting shards capacity>>.
+
 [discrete]
 [[troubleshooting-max-docs-limit]]
 ==== Number of documents in the shard cannot exceed [2147483519]