17755: Merge branch 'main' into 17755-add-singularity-to-compute-image

[arvados.git] / doc / admin / storage-classes.html.textile.liquid

diff --git a/doc/admin/storage-classes.html.textile.liquid b/doc/admin/storage-classes.html.textile.liquid
index 1a6420d4c48bfe5bbacfba10a72313bc53bec3ee..3e17831b58d6d32f21b0c278253aea4394334fac 100644 (file)
--- a/doc/admin/storage-classes.html.textile.liquid
+++ b/doc/admin/storage-classes.html.textile.liquid
@@ -15,19 +15,15 @@ Storage classes (alternately known as "storage tiers") allow you to control whic
 The storage classes for each volume are set in the per-volume "keepstore configuration":{{site.baseurl}}/install/install-keepstore.html
 
 <pre>
-Volumes:
- - ... Volume configuration ...
-   #
-   # If no storage classes are specified, will use [default]
-   #
-   StorageClasses: null
-
- - ... Volume configuration ...
-   #
-   # Specify this volume is in the "archival" storage class.
-   #
-   StorageClasses: [archival]
-
+    Volumes:
+      ClusterID-nyw5e-000000000000000:
+        # This volume is in the "default" storage class.
+        StorageClasses:
+          default: true
+      ClusterID-nyw5e-000000000000001:
+        # Specify this volume is in the "archival" storage class.
+        StorageClasses:
+          archival: true
 </pre>
 
 Names of storage classes are internal to the cluster and decided by the administrator.  Aside from "default", Arvados currently does not define any standard storage class names.
@@ -38,10 +34,10 @@ h3. Using storage classes
 
 h3. Storage management notes
 
-The "keep-balance":{{site.baseurl}}/install/install-keep-balance.html service is responsible for deciding which blocks should be placed on which keepstore volumes.  As part of the rebalancing behavior, it will determine where a block should go in order to satisfy the desired storage classes, and issue pull requests to copy the block from its original volume to the desired volume.  The block will subsequently be moved to trash on the original volume.
+When uploading data, if a data block cannot be uploaded to all desired storage classes, it will result in a fatal error.  Data blocks will not be uploaded to volumes that do not have the desired storage class.
 
-If a block appears in multiple collections with different storage classes, the block will be stored in separate volumes for each storage class, even if that results in overreplication, unless there is a volume which has all the desired storage classes.
+If you change the storage classes for a collection, the data is not moved immediately.  The "keep-balance":{{site.baseurl}}/install/install-keep-balance.html service is responsible for deciding which blocks should be placed on which keepstore volumes.  As part of the rebalancing behavior, it will determine where a block should go in order to satisfy the desired storage classes, and issue pull requests to copy the block from its original volume to the desired volume.  The block will subsequently be moved to trash on the original volume.
 
-If a collection has a desired storage class which is not available in any keepstore volume, the collection's blocks will remain in place, and an error will appear in the @keep-balance@ logs.
+If a block is assigned to multiple storage classes, the block will be stored on @desired_replication@ number of volumes for storage class, even if that results in overreplication.
 
-This feature does not provide a hard guarantee on where data will be stored.  Data may be written to default storage and moved to the desired storage class later.  If controlling data locality is a hard requirement (such as legal restrictions on the location of data) we recommend setting up multiple Arvados clusters.
+If a collection has a desired storage class which is not available in any keepstore volume, the collection's blocks will remain in place, and an error will appear in the @keep-balance@ logs.