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.

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

Note

Typically, node I/O may be a bottleneck in clusters with cache on SSD or all-SSD setups.

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.