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Monitoring disk space on volumes with LUNs that do not use Snapshot copies

This example illustrates how to monitor disk space on a volume when you create a LUN without using Snapshot copies.

About this task

For this example, assume that you require less than the minimum capacity based on the recommendation of creating a seven-disk volume.

For simplicity, assume the LUN requires only three GB of disk space. For a traditional volume, the volume size must be approximately three GB plus 10 percent. The recommended volume size is approximately 2*3 GB plus the rate of change of data.

Steps

  1. From the storage system, create a new traditional volume named volspace that has approximately 67 GB, and observe the effect on disk space by entering the following commands: vol create volspace aggr1 67gdf -r /vol/volspace
    The following sample output is displayed. There is a snap reserve of 20 percent on the volume, even though the volume is used for LUNs, because snap reserve is set to 20 percent by default.
    Filesystem              kbytes    used       avail   reserved     Mounted on
    /vol/volspace           50119928  1440     50118488         0     /vol/volspace/
    /vol/volspace/.snapshot 12529980     0     12529980         0     /vol/volspace/.snapshot
  2. Set the percentage of snap reserve space to 0 and observe the effect on disk space by entering the following commands: snap reserve volspace 0df -r /vol/volspace
    The following sample output is displayed. The amount of available Snapshot copy space becomes zero, and the 20 percent of Snapshot copy space is added to available space for /vol/volspace.
    Filesystem                kbytes    used       avail   reserved   Mounted on
    /vol/volspace/          62649908    1440    62648468          0  /vol/volspace/
    /vol/volspace/.snapshot        0       0           0          0  /vol/volspace/.snapshot
  3. Create a LUN named /vol/volspace/lun0 and observe the effect on disk space by entering the following commands: lun create -s 3g -t aix /vol/volspace/lun0 df -r /vol/volspace
    The following sample output is displayed. Three GB of space is used because this is the amount of space specified for the LUN, and LUN space reservation is enabled by default.
    Filesystem               kbytes      used       avail   reserved   Mounted on
    /vol/volspace/           62649908   3150268    59499640        0   /vol/volspace/
    /vol/volspace/.snapshot         0         0           0        0   /vol/volspace/.snapshot
  4. Create an igroup named aix_host and map the LUN to it by entering the following commands (assuming that the host node name is iqn.1996-04.aixhost.host1). Depending on your host, you might need to create WWNN persistent bindings. These commands have no effect on disk space. igroup create -i -t aix aix_host iqn.1996-04.aixhost.host1lun map /vol/volspace/lun0 aix_host 0
  5. From the host, discover the LUN, format it, make the file system available to the host, and write data to the file system. For information about these procedures, see your Host Utilities documentation. These commands have no effect on disk space.
  6. From the storage system, ensure that creating the file system on the LUN and writing data to it has no effect on space on the storage system by entering the following command: df -r /vol/volspace
    The following sample output is displayed. From the storage system, the amount of space used by the LUN remains 3 GB.
    Filesystem              kbytes          used      avail   reserved   Mounted on
    /vol/volspace/          62649908     3150268   59499640        0     /vol/volspace/
    /vol/volspace/.snapshot        0           0          0        0     /vol/volspace/.snapshot
  7. Turn off space reservations and see the effect on space by entering the following commands: lun set reservation /vol/volspace/lun0 disabledf -r /vol/volspace
    The following sample output is displayed. The 3 GB of space for the LUN is no longer reserved, so it is not counted as used space; it is now available space. Any other requests to write data to the volume can occupy all of the available space, including the 3 GB that the LUN expects to have. If the available space is used before the LUN is written to, write operations to the LUN fail. To restore the reserved space for the LUN, turn space reservations on.
    Filesystem              kbytes     used       avail   reserved     Mounted on
    /vol/volspace/          62649908    144    62649584          0     /vol/volspace/
    /vol/volspace/.snapshot        0      0           0          0     /vol/volspace/.snapshot