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Control Center application data storage requirements

Control Center uses an LVM thin pool to store tenant (application) data. LVM thin pools include separate storage areas for data and for metadata. For each tenant it manages, Control Center maintains a separate virtual device (a volume) in the data storage area of its LVM thin pool. Also, Control Center creates virtual devices in the data storage area for snapshots of tenant data.

To ensure consistency, Control Center requires the following, minimum amount of free space in its thin pool:

  • 3GiB available for each tenant volume
  • 3GiB available in the data storage area
  • 62MiB available in the metadata storage area
  • The total amount of metadata storage must be 1% of total data storage

In addition, the ratio of application data stored in the thin pool to the total amount of storage in the pool should always be 50%. When the amount of available space is less than double the amount of total storage, the snapshot feature is prone to failure.

Examining application data storage status

Beginning with release 1.3.0, Control Center initiates an emergency shutdown when the minimum required amounts of free space are not available in the serviced thin pool or tenant volumes.

Use this procedure to display the amount of free space in a Control Center thin pool and tenant volumes, to determine how much space is available in the LVM volume group that contains the thin pool, and to determine whether additional steps are required.

  1. Log in to the master host as root or as a user with superuser privileges.

  2. Display the amount of space available in the serviced thin pool.

    serviced volume status

    Example output with highlighted values:

    Status for volume /opt/serviced/var/volumes:

    Driver: devicemapper Driver Type: direct-lvm Volume Path: /opt/serviced/var/volumes

    Thin Pool --------- Logical Volume: serviced-serviced--pool Metadata (total/used/avail): 2.2 GiB / 64.18 MiB (2.85%) / 2.137 GiB (97.15%) Data (total/used/avail): 200 GiB / 30.576 GiB (15%) / 169.424 GiB (85%)

    3ir81rg1h8b09ipowynz3qx2f Application Data ----------------------------------------- Volume Mount Point: /opt/serviced/var/volumes/3ir81rg1h8b09ipowynz3qx2f Filesystem (total/used/avail): 98.31 GiB / 1.511 GiB (1.5%) / 91.78 GiB (93%) Virtual device size: 100 GiB

    The result includes detailed information about the serviced thin pool and each tenant volume.

    • If the amount of free space in the serviced thin pool is sufficient, stop. No further action is required.
    • If the amount of free space in the data or metadata portions of the serviced thin pool is not sufficient, perform the following steps.
    • Identify the volume group to which the serviced thin pool belongs.
    lvs --options=lv_name,vg_name,lv_size

    The volume group associated with serviced-pool contains the serviced thin pool.

  3. Display the amount of free space in the volume group that contains the serviced thin pool.

    Replace Volume-Group with the name of the volume group identified in the previous step:

    vgs --no-headings --options=vg_free Volume-Group
    • If the amount of free space in the volume group is not sufficient to increase one or both of the storage areas of the serviced thin pool to their required minimums, add physical or logical storage to the volume group. For more information, refer to your operating system documentation.
    • If the amount of free space in the volume group is sufficient to increase one or both of the storage areas of the serviced thin pool to their required minimums, proceed to the next step.
    • Increase the free space in one or both areas of the serviced thin pool.
    • To increase the amount of space in the metadata area, proceed to Adding space to the metadata area of a Control Center thin pool.
    • To increase the amount of space in the data area, proceed to Adding space to the data area of a Control Center thin pool.