Seagate Kinetic Open Storage Project Plugfest

Open vStorage was invited to host a session during the Seagate Kinetic plugfest on Tuesday, September 20 to demo and discuss advances in Ethernet-connected storage. Kinetic is a drive architecture in which the drive is a key/value server with Ethernet connectivity. With Open vStorage we have created ALBA ASD software that mimics this key/value behaviour for normal SATA drives. Kinetic drives can of course also be used as archiving backend for an Open vStorage cluster.

Read more about the Kinetic Open Storage Project here.

Edge: HA, failure and the moving of volumes explained

edge HA FailoverOpen vStorage is designed to be rock solid and survive failures. These failures can come in many forms and shapes: nodes might die, network connections might get interrupted, … Let’s give an overview of the different tactics that are used by Open vStorage when disaster strikes by going over some possible use cases where the new edge plays a role.

Use case 1: A hypervisor fails

In case the hypervisor fails, the hypervisor management (OpenStack, vCenter, …) will detect the failure and restart the VM on another hypervisor. Since the VM is started on another hypervisor, the VM will talk to the edge client on the new hypervisor. The edge client will connect to a volume driver in the vPool and enquire which volume driver owns the disks of the VM. The volume driver responds who is the owner and the edge connects to the volume driver owning the volume. This all happens almost instantaneously and in the background so the the IO of the VM isn’t affected.

Use case 2: A Storage Router fails

In case a Storage Router and hence the volume driver on it die, the edge client automatically detects that the connection to the volume driver is lost. Luckily the edge keeps a list of volume drivers which also serve the vPool and it connects to one of the remaining volume drivers in the vPool. It is clear that the edge prefers to fail-over to a volume driver which is close-by f.e. within the same datacenter. The new volume driver to which the edge connects detects that it isn’t the owner of the volume. As the old volume driver is no longer online, the new volume driver steals the ownership of the VMs volume. Stealing is allowed in this case as the old volume driver is down. Once the new volume driver becomes the owner of the volumes, the edge client can start serving IO. This whole process process happens in the background and halts the IO of the VM for a fraction of a second.

Use case 3: Network issues

In some exceptional cases it isn’t the hypervisor or the storage router that fails but the network in between. This is an administrator’s worst nightmare as it might lead to split brain scenarios. Even in this case the edge is able to outlive the disaster. As the network connection between the edge and the volume driver is lost, the edge will assume the volume driver is dead. Hence, as in use case 2 the edge connects to another volume driver in the same vPool. The volume driver first tries to contact the old volume driver.

Now there are 2 options:

  • The new volume driver can contact the old volume driver. After some IO is exchanged the new volume driver asks the old volume driver to hand over the volume. This handover doesn’t impact the edge.
  • The new volume driver can also not contact the old volume driver. In that case old volume driver steals the volume from the old volume driver. It does this by updating the ownership of the volume in the distributed DB and by uploading a new key to the backend. As the ALBA backend uses a conditional write approach, it only writes the IO to disks of the backend if the accompanying key is valid, it can ensure only the new volume driver is allowed to write to the backend. If the old volume driver would still be online (split brain) and try to update the backend, the write would fail as it is using an outdated key.

IT Administrator – Fargo – Hot and fresh

IT Administrator Fargo - Heis und freshThe new Fargo release of Open vStorage is featured in the German IT Administrator magazine of December. The IT Administrator team did a deep dive of almost 5 pages into the new Fargo architecture and gave the new release a testdrive through Ansible and docker.

Open vStorage erhält mit dem neuen Fargo-Release eine völlig überarbeitete Architektur. Die quelloffene Storage-Umgebung macht sich den Shared-Memory-Ansatz zunutze und verspricht noch mehr Leistungsfähigkeit, eine bessere Performance und ein Höchstmaß an Sicherheit. Damit ist Open vStorage die ideale Lösung für Multi-Petabyte Multi-Datacenter Storage-Cluster – so sehen das zumindest die Entwickler.