Chapter 6. Ceph File System quotas

Limitations

• CephFS quotas rely on the cooperation of the client mounting the file system to stop writing data when it reaches the configured limit. However, quotas alone cannot prevent an adversarial, untrusted client from filling the file system.
• Once processes that write data to the file system reach the configured limit, a short period of time elapses between when the amount of data reaches the quota limit, and when the processes stop writing data. The time period generally measures in the tenths of seconds. However, processes continue to write data during that time. The amount of additional data that the processes write depends on the amount of time elapsed before they stop.
• When using path-based access restrictions, be sure to configure the quota on the directory to which the client is restricted, or to a directory nested beneath it. If the client has restricted access to a specific path based on the MDS capability, and the quota is configured on an ancestor directory that the client cannot access, the client will not enforce the quota. For example, if the client cannot access the /home/ directory and the quota is configured on /home/, the client cannot enforce that quota on the directory /home/user/.
• Snapshot file data that has been deleted or changed does not count towards the quota.
• No support for quotas with NFS clients when using setxattr, and no support for file-level quotas on NFS. To use quotas on NFS shares, you can export them using subvolumes and setting the --size option.

Prerequisites

• Root-level access to the Ceph client node.
• The attr package is installed.

Prerequisites

• Root-level access to the Ceph client node.
• The attr package is installed.

Procedure

• Set the quota for a direcotry by using a byte-limit quota:

  Note

  The following values are supported for byte-limit quota: K, Ki, M, Mi, G, Gi, T, and Ti.

  Syntax

  setfattr -n ceph.quota.max_bytes -v LIMIT_VALUE DIRECTORY

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  Example

  [root@client ~]# setfattr -n ceph.quota.max_bytes -v 2T /cephfs/

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• Set the quota for a directory by using a file-limit quota:

  Syntax

  setfattr -n ceph.quota.max_files -v LIMIT_VALUE DIRECTORY

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  Example

  [root@client ~]# setfattr -n ceph.quota.max_files -v 10000 /cephfs/

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  In this example, 10000 equals 10,000 files.

  Note

  Only numerical values are supported for the file LIMIT_VALUE.

Prerequisites

• Root-level access to the Ceph client node.
• Make sure that the attr package is installed.