Volume Placement (Preview)

With Volume Placement, you can specify which failure domain to place a volume on upon its creation. The idea behind volume placement is to statically define, separate, and manage how volumes and data can tolerate a failure and provide availability - through failure of a server or Availability Zone. By default, Lightbits will define server-level failure domains and in Multi AZ deployments in Azure also zone level failure domains. In order to reduce IO latency and reduce intra-zone traffic it is recommended to deploy volumes where the primary replication is in the same zone as the VM's that are using the volume.

Volume placement is only relevant for Lightbits SDS clustered deployed in MultiAZ. In single AZ deployments, Volume placement is not relevant.

When you set the affinity of a volume to a specific zone this means that the clusters algorithm that selects where to position the Volume with it's replicas (Primary and 2 replicas) the Primary will always be in the affinity zone. During the life-cycle of the cluster there are cases (not frequent) where the cluster will need to move volumes between nodes in order to keep the cluster balanced. At this stage when the volume is moved the affinity is not always kept and the volumes primary copy may migrate to another zone.

During a failure scenario where a server or a zone are down the primary may move to a different zone temporarily until the Server in the original location is rebuilt (and then the primary will move back to the correct zone)

Note that this feature is associated with the create volume command.

Current feature limitations of Volume Placement include the following:

• Only failure domain labels are currently matched (e.g., primaryfd:zone-2)
• Volume Placement cannot be specified for a clone (a clone is always placed on the same nodes as the parent volume/snapshot).

lbcli create volume with volume 'placement-affinity'

lbcli -J $JWT create volume ----name=vol1 --acl=acl1 --size="4 Gib" --replica-count=3 --placement-affinity="primaryfd:zone-2"

In the example above, the Primary replica of the volume will be placed in Zone2.