7.9. Managing Fast Path¶

Fast path is a feature that may boost Virtuozzo Storage read performance if node I/O is a bottleneck. In previous versions of Virtuozzo Storage, performance could be limited by node I/O being handled in a single thread in user space. In the current version of Virtuozzo Storage, fast path is enabled by default and I/O is handled using multi-threading in kernel space, which eliminates unnecessary context switches and improves performance.

If node I/O is a bottleneck, fast path may increase maximum node read performance up to 3 times in some cases.

Fast path is enabled by default. It is managed by the kdirect.enable parameter in /etc/vstorage/vstorage-mount.conf.

Ways to disable the feature differ depending on whether or not you use the GUI.

To disable fast path on a GUI-enabled deployment, do the following on each node:

1. Set ‘kdirect.enable’ to 0 in ‘/etc/vstorage/vstorage-mount.conf’.

2. Stop all VEs on the node or migrate them to another node using prlctl migrate or Virtuozzo Automator.

3. Stop the vstorage-ui-agent service:

   # systemctl stop vstorage-ui-agent.service
   

4. Unmount the storage location:

   # umount /vstorage/<cluster_name>
   

5. Start the vstorage-ui-agent service again:

   # systemctl start vstorage-ui-agent.service
   

   The service will re-mount the storage location automatically.

6. Migrate all VEs back.

To disable fast path on a deployment without GUI, do the following on each node:

1. Set ‘kdirect.enable’ to 0 in ‘/etc/vstorage/vstorage-mount.conf’.

2. Stop all VEs on the node or migrate them to another node using prlctl migrate or Virtuozzo Automator.

3. Unmount and re-mount the storage location:

   # umount /vstorage/<cluster_name>
   # mount -a /vstorage/<cluster_name>
   

4. Migrate all VEs back.