Configuring virtual disks

Plumbery has the ability to adjust virtual disks attached to a node, like in the following example:

nodes:

  - myServer:

      disks:

        # resize system disk to 80 GB
        #
        - 0 80

        # add a 100 GB disk for economy storage
        #
        - 1 100 economy

Components of each disks: directive

Component	Required	Description
disk id	yes	An integer between 0 and 9. The value 0 designates the system disk
size in GB	yes	An integer between 10 and 1000
class of storage	no	Either standard (default) or highperformance or economy

How to partition and configure virtual disks?

Any change of virtual disks made at the infrastructure level has to be reflected into the operating system itself. For example, explicit decision is required on number and sizes of partitions. You may want to use one file system or another, depending of requirements for the storage sub-system. In case of storage virtualisation, there is also an option to combine multiple virtual disks in a single logical volume and file system.

Cloud-config can be a convenient Trojan horse to perform such tasks, as demonstrated in following examples.

How to resize system disk of a Linux server?

LVM is used for Ubuntu standard images, so the resizing of system disk is quite easy.

nodes:

  - myServer:

      appliance: 'Ubuntu 14'

      # augment system disk
      #
      disks:
        - 0 50 standard

      cloud-config:

        runcmd:

          - echo "===== Growing LVM with expanded disk"
          - lvextend -l +100%FREE /dev/mapper/rootvol00-rootlvol00
          - resize2fs /dev/mapper/rootvol00-rootlvol00

How to add high-performance storage on Linux?

This case is a bit more complicated because of the partitioning, etc. Hopefully cloud-config can help us to push some scripts to the target node and to execute them.

nodes:

  - myServer:

      appliance: 'Ubuntu 14'

      # add a disk from high-performance tier of storage
      #
      disks:
        - 1 100 highperformance

      cloud-config:

        write_files:

          - path: /root/set_pdisk.sh
            content: |
              #!/usr/bin/env bash
              if [ ! -b ${1}1 ]; then
              echo "===== Partioning ${1}"
              cat <<EOF | fdisk ${1}
              n
              p
              1


              t
              8e
              w
              EOF
              echo "===== Creating LVM physical disk ${1}1"
              pvcreate ${1}1
              fi


          - path: /root/set_vdisk.sh
            content: |
              #!/usr/bin/env bash
              if [ -z "$(blkid ${1})" ];
              then
                  echo "===== Formatting ${1}"
                  mkfs -t ${2} ${1}
              fi
              UUID=$(blkid ${1} | sed -n 's/.*UUID=\"\([^\"]*\)\".*/\1/p')

              if ! grep -q "${UUID}" /etc/fstab; then
                  echo "===== Adding ${1} to fstab"
                  LINE="UUID=\"${UUID}\"\t${3}\t${2}\tnoatime,nodiratime,nodev,noexec,nosuid\t1 2"
                  echo -e "${LINE}" >> /etc/fstab
              fi

              echo "===== Mounting ${3}"
              [ -d "${3}" ] || mkdir -p "${3}"
              mount "${3}"

        runcmd:

          - echo "===== Handling additional disk"
          - chmod +x /root/set_pdisk.sh
          - /root/set_pdisk.sh /dev/sdb

          - echo "===== Configuring /dev/sdb1 for high-performance storage"
          - vgcreate highperformancevg /dev/sdb1
          - lvcreate -l 100%FREE -n highperformancelv highperformancevg
          - chmod +x /root/set_vdisk.sh
          - /root/set_vdisk.sh /dev/highperformancevg/highperformancelv ext4 /highperformance

After complete configuration, everything written to /highperformance will benefit from best performance levels.