Update shell-and-data-access.md

docs.it4i/general/shell-and-data-access.md

@@ -108,6 +108,8 @@ After logging in, you will see the command prompt with the name of the cluster a
 
 ## Data Transfer
 
+### Serial Transfer
+
 Data in and out of the system may be transferred by SCP and SFTP protocols.
 
 | Cluster  | Port | Protocol  |
@@ -133,6 +135,14 @@ or
 local $ sftp -o IdentityFile=/path/to/id_rsa username@cluster-name.it4i.cz
 ```
 
+You may request the **aes256-gcm@openssh.com cipher** for more efficient ssh based transfer:
+
+```console
+local $ scp -c aes256-gcm@openssh.com -i /path/to/id_rsa -r my-local-dir username@cluster-name.it4i.cz:directory
+```
+
+The -c argument may be used with ssh, scp and sftp, and is also applicable to sshfs and rsync below.
+
 A very convenient way to transfer files in and out of the cluster is via the fuse filesystem [SSHFS][b].
 
 ```console
@@ -159,9 +169,11 @@ local $ rsync my-local-file
 local $ rsync -r my-local-dir username@cluster-name.it4i.cz:directory
 ```
 
+### Parallel Transfer
+
 !!! note
-    The data transfer speed is limited by the single-core ssh encryption speed to about **150 MB/s**
-    Run **multiple rsync** instances for unlimited transfers
+    The data transfer speed is limited by the single-core ssh encryption speed to about **250 MB/s** (750 MB/s in case of aes256-gcm@openssh.com cipher)
+    Run **multiple** instances for unlimited transfers
 
 Parallel execution of multiple rsync processes utilizes multiple cores to accelerate encryption and multiple tcp streams for enhanced bandwidth.
 First, set up ssh-agent single sign on: