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Run Dependencies

BSUd is only for Linux-based OS on Outscale's cloud for now.

BSUd will need to run those external commands:

Configuration

config.json

BSUd is configured through a json configuration file. The following section describe a simple configuration (see config.json):

  • authentification
    • access-key: optional if OSC_ACCESS_KEY env var is set.
    • secret-key: optional if OSC_SECRET_KEY env var is set.
  • drives
    • name: unique drive's name. Be sure to use an unique name across your Outscale account otherwise, BSUd cannot differentiate drives and will try to attach them.
    • target: between "online" (default), "offline" and "delete".
    • disk-type: kind of BSU to use between "gp2", "io1" or "standard".
    • mount-path: absolute path where BSUd will mount the scaled file system.
    • disk-iops-per-gib: BSU iops to allocate per GibiBytes (for io1 disks).
    • max-total-size-gib: Limit the maximal size a drive can offer.
    • disk-scale-factor-perc: Controls the size of the next BSU to be created regarding the size of the largest or smallest existing BSU in the drive.
    • min-used-space-perc controls when to scale down (remove a BSU) accordingly to the used percentage in the drive.
    • max-bsu-count: maximal allowed number of BSU in the drive.

Environment variables

  • OSC_ACCESS_KEY
  • OSC_SECRET_KEY

Usage

  • Get version: bsud --version
  • Manually run bsud: bsud -c docs/config.json

bsud will look for /etc/osc/bsud.json configuration file path by default.

Creating or updating a drive

Just add or edit drive in BSUd configuration and restart daemon. Note that changing drive name is not supported for now and will just create a new fresh drive.

About drive targets

When drive target is configured to "online" (default), all BSU are attached and the drive is maintained available to user.

Drives which have a "offline" target are unmounted and all its BSUs are detached from the VM.

Drives which have a "delete" target are umounted, all its BSU are detached from the VM and all its BSU are deleted.

About auto-scaling

BSUd is using exponential auto-scaling. It will create an exponentially larger BSU to expand the drive while limiting the number of attached BSU. The size of created BSU will be adjusted depending of a scaling factor (see disk-scale-factor-perc).

Example: If the largest BSU in the drive is 20Gib and the scale factor is set to 10%, then the next BSU to be added to the drive will be will be 20 * 1.1 = 22Gib.

BSUd may also create BSU which are 10% smaller in some particular cases in order to balance drive size repartition. More details on how this can occur in dev documentation.

A minimal and maximal space usage can be defined in order to trigger scaling (see min-used-space-perc and max-used-space-perc).

Example: If the drive is 89% full and the max-used-space-perc is set to 85%, then the drive will scale up (adding a BSU). Example: If the drive is 19% full and the min-used-space-perc is set to 20%, then the drive will scale down (remove a BSU).

VMs cannot attach an infinite number of disks. max-bsu-count will limit the number of attached BSU without limiting drive's maximal size. BSUd will scale up and migrate any data before removing a BSU. BSUd will maintain max-bsu-count minus 1 in order to be able to add one more disk to scale up. Once max-bsu-count BSU reached, BSUd will try to remove the smallest disk.