docs: Add backup and restore doc for VictoriaLogs

This commit adds doc for VictoriaLogs backup and restore based on `rsync`.

docs/VictoriaLogs/README.md

@@ -129,6 +129,55 @@ For example, the following command starts VictoriaLogs, which stores the data at
 
 VictoriaLogs automatically creates the `-storageDataPath` directory on the first run if it is missing.
 
+## Backup and restore
+
+VictoriaLogs currently does not have a snapshot feature and a tool like vmbackup as VictoriaMetrics does.
+So backing up VictoriaLogs requires manually executing the `rsync` command.
+
+The files in VictoriaLogs have the following properties:
+- All the data files are immutable. Small metadata files can be modified.
+- Old data files are periodically merged into new data files.
+
+Therefore, for a complete data **backup**, you need to run the `rsync` command **twice**.
+
+```sh
+# example of rsync to remote host
+rsync -avh --progress <path-to-victorialogs-data> <username>@<host>:<path-to-victorialogs-backup>
+```
+
+The first `rsync` will sync the majority of the data, which can be time-consuming.
+As VictoriaLogs continues to run, new data is ingested, potentially creating new data files and modifying metadata files.
+
+```sh
+# example output
+sending incremental file list
+victoria-logs-data/
+victoria-logs-data/flock.lock
+              0 100%    0.00kB/s    0:00:00 (xfr#1, to-chk=78/80)
+              
+...
+
+victoria-logs-data/partitions/20240809/indexdb/17E9ED7EF89BF422/metaindex.bin
+             51 100%    5.53kB/s    0:00:00 (xfr#64, to-chk=0/80)
+
+sent 12.19K bytes  received 1.30K bytes  3.86K bytes/sec
+total size is 7.31K  speedup is 0.54
+```
+
+The second `rsync` **requires a brief shutdown of VictoriaLogs** to ensure all data and metadata files are consistent and no longer changing.
+This `rsync` will cover any changes that have occurred since the last `rsync` and should not take a significant amount of time.
+
+To **restore** from a backup, simply `rsync` the backup files from a remote location to the original directory during downtime.
+VictoriaLogs will automatically load this data upon startup.
+
+```sh
+# example of rsync from remote backup to local
+rsync -avh --progress <username>@<host>:<path-to-victorialogs-backup> <path-to-victorialogs-data>
+```
+
+It is also possible to use **the disk snapshot** in order to perform a backup. This feature could be provided by your operating system,
+cloud provider, or third-party tools. Note that the snapshot must be **consistent** to ensure reliable backup.
+
 ## Multitenancy
 
 VictoriaLogs supports multitenancy. A tenant is identified by `(AccountID, ProjectID)` pair, where `AccountID` and `ProjectID` are arbitrary 32-bit unsigned integers.