update: docs about using azure storage account as storage. (#4152)

Signed-off-by: charles-woshicai <583605554@qq.com>

Co-authored-by: Charles Cai <charles.cai@sap.com>

docs/sources/storage/_index.md

@@ -68,6 +68,10 @@ DynamoDB is susceptible to rate limiting, particularly due to overconsuming what
 
 BoltDB is an embedded database on disk. It is not replicated and thus cannot be used for high availability or clustered Loki deployments, but is commonly paired with a `filesystem` chunk store for proof of concept deployments, trying out Loki, and development. The [boltdb-shipper](../operations/storage/boltdb-shipper/) aims to support clustered deployments using `boltdb` as an index.
 
+### Azure Storage Account
+
+An Azure storage account contains all of your Azure Storage data objects: blobs, file shares, queues, tables, and disks.
+
 ## Schema Configs
 
 Loki aims to be backwards compatible and over the course of its development has had many internal changes that facilitate better and more efficient storage/querying. Loki allows incrementally upgrading to these new storage _schemas_ and can query across them transparently. This makes upgrading a breeze. For instance, this is what it looks like when migrating from the v10 -> v11 schemas starting 2020-07-01:
@@ -281,3 +285,33 @@ schema_config:
         prefix: index_
         period: 24h
 ```
+
+### Azure Storage Account
+
+```yaml
+schema_config:
+  configs:
+  - from: "2020-12-11"
+    index:
+      period: 24h
+      prefix: index_
+    object_store: azure
+    schema: v11
+    store: boltdb-shipper
+  storage_config:
+    azure:
+      # For the account-key, see docs: https://docs.microsoft.com/en-us/azure/storage/common/storage-account-keys-manage?tabs=azure-portal
+      account_key: <account-key>
+      # Your azure account name
+      account_name: <account-name>
+      # See https://docs.microsoft.com/en-us/azure/storage/blobs/storage-blobs-introduction#containers
+      container_name: <container-name>
+      request_timeout: 0
+    boltdb_shipper:
+      active_index_directory: /data/loki/boltdb-shipper-active
+      cache_location: /data/loki/boltdb-shipper-cache
+      cache_ttl: 24h
+      shared_store: azure
+    filesystem:
+      directory: /data/loki/chunks
+```