Add warning about increased disk usage during physical backup (#191)

* Update physical.md * Update start-backup.md
percona · Aug 5, 2024 · 3f29dc7 · 3f29dc7
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diff --git a/docs/features/physical.md b/docs/features/physical.md
@@ -7,6 +7,10 @@
 *  Percona Server for MongoDB starting from versions 4.2.15-16, 4.4.6-8, 5.0 and higher. 
 * WiredTiger is used as the storage engine in Percona Server for MongoDB, since physical backups heavily rely on the WiredTiger [`$backupCursor` :octicons-link-external-16:](https://docs.percona.com/percona-server-for-mongodb/6.0/backup-cursor.html) functionality.
 
+!!! warning 
+
+    During the period the backup cursor is open, database checkpoints can be created, but no checkpoints can be deleted. This may result in significant file growth.
+
 !!! admonition "See also"
 
     Percona Blog

diff --git a/docs/usage/start-backup.md b/docs/usage/start-backup.md
@@ -38,7 +38,11 @@
      ```
 
      During a *physical* backup, Percona Backup for MongoDB  copies the contents of the `dbpath` directory (data and metadata files, indexes, journal and logs) from every shard and config server replica set to the backup storage. 
+     
+    !!! warning 
 
+        During the period the backup cursor is open, database checkpoints can be created, but no checkpoints can be deleted. This may result in significant file growth.
+
      Starting with [2.4.0](../release-notes/2.4.0.md), PBM doesn't stop [point-in-time recovery oplog slicing](../features/point-in-time-recovery.md#oplog-slicing), if it's enabled, but runs it in parallel. This ensures [point-in-time recovery](pitr-tutorial.md) to any timestamp if it takes too long (e.g. hours) to make a backup snapshot.
 
 === ":material-select-multiple: Selective"