3.2. Configuring Chunk Servers

This section explains how to complete the following tasks:

  • Increase disk space in a cluster by adding new chunk servers to it
  • Remove chunk servers from a cluster for performing maintenance tasks on them

3.2.1. Adding New Chunk Servers to Increase Disk Space

You can increase the amount of disk space in a Virtuozzo Storage cluster simply by adding new chunk servers to it. For details, see Setting Up Chunk Servers.

Note

Virtuozzo Storage can scale to support at least 8 PB of effective available disk space, which means up to 24 PB of physical disk space in the case of mirroring with 3 copies.

3.2.2. Removing Chunk Servers

If you need to remove a chunk server from the cluster, for example, to perform some maintenance tasks on it, do the following:

  1. Make sure that

    • The number of chunk servers configured for your cluster is enough to store the required number of data chunks (that is, equals or exceeds the current replication value).
    • The chunk servers have enough disk space to store the chunks. For instructions on obtaining this information, see Monitoring Chunk Servers.
  2. Find out the index number of the chunk server you want to remove by running the following command on some of your cluster servers:

    # vstorage -c stor1 top
    

    This will display detailed information about the stor1 cluster. Locate the section with the information about chunk servers, for example:

    ...
     CSID  STATUS     SPACE   FREE REPLICAS IOWAIT IOLAT(ms) QDEPTH HOST
     1025  active     105GB   88GB       40     0%       0/0    0.0 10.30.17.38
     1026  active     105GB   88GB       40     0%       0/0    0.0 10.30.18.40
     1027  active     105GB   99GB       40     0%       0/0    0.0 10.30.21.30
     1028  active     107GB  101GB       40     0%       0/0    0.0 10.30.16.38
    ...
    

    The CSID column displays the index number of chunk servers. In the output above, four chunk servers are configured for the stor1 cluster. They have index numbers of 1025, 1026, 1027, and 1028.

  3. Remove the chunk server from the cluster. For example, to delete the chunk server with index number 1028 from the stor1 cluster, run this command:

    # vstorage -c stor1 rm-cs --wait 1028
    

Once you initiate the delete operation, the cluster starts replicating data chunks that were stored on the removed server and placing them on the remaining chunk servers in the cluster. The --wait option, when specified, tells the command to wait until the operation is complete (which may take a long time).

Note

  1. If the CS’s disk has disappeared from the OS and the CS has no access to its repository, data chunks which need to be replicated will not be accessible and CS removal will not complete. You will need to forcibly remove the CS from the cluster with the -f option. Warning: Do so only if the CS is irreversibly lost. Never remove active chunk servers with the -f option.
  2. When deletion is in progress, you can cancel it with the command vstorage -c stor1 rm-cs --cancel 1028. This might be useful, for example, if you specified a wrong ID of the chunk server to remove.

To add a removed chunk server back to the cluster, set it up from scratch by following the steps in Setting Up Chunk Servers.