How to Survive an OpenStack Cloud Meltdown with Ceph

OpenStack Summit | Vancouver 2018
How to Survive an OpenStack Cloud
Meltdown with Ceph
Federico Lucifredi, Sean Cohen, Sébastien Han
OpenStack Summit Vancouver
May 22, 2018

OpenStack Summit | Vancouver 2018OpenStack Summit | Vancouver 2018
What’s the Problem?

DatacenterDynamics
https://bit.ly/2IEC3t4

@hohocho
https://bit.ly/2IVor0b
TWS
https://bit.ly/2IAQXVv
Additional coverage
DataCenter
Knowledge
https://bit.ly/2x32Iyn

S3 Service Disruption
https://amzn.to/2melOup

Redefining Disaster Recovery
● The problem space
○ Disaster recovery (DR)
○ High availability (HA)
○ Fault tolerance (FT)
○ And everyone’s favorite… Backup.
● Key metrics
○ Recovery point objective (RPO)
○ Recovery time objective (RTO)

Cloud Meltdown Prevention
State of the art

Different failure domains
Ways to segregate your data:
● Ceph and failure domains:
○ Always build redundancy from racks (1 replica per rack)
○ Go as granular as you want (room, pod, pdu, row, rack...)
○ Between pools
● Different Ceph clusters in the same datacenter, but different facility
● Different Ceph clusters geographically spread

Nova and Cinder snapshots
Operational Recovery (Human error, Database
corruptions, Malicious code etc…)
● NOT a backup, just for convenience
● Difference:
○ Nova: new image in Glance
○ Cinder: internal snapshot with layering
● Snapshot are fast and transparent, no data moving
the network
● Always use a qemu-guest-agent in your virtual
machine

Cinder Ceph backup
● Efficient Ceph to Ceph backups
● Always incremental - block differential
● Works between:
○ Ceph Pools (not recommended)
○ Ceph clusters
● Deeper Workload backup with change
block tracking based style on RBD Diff,
available via 3rd party vendors

Disaster Recovery with RBD Mirroring

RBD Mirroring - Ceph Jewel
Ceph Jewel release (Apr 2016):
● Added ‘rbd-mirror’ daemon to synchronise Ceph images from one cluster to another
● Relies on two new RBD image features:
○ journaling: enables journaling for every transaction on the image
○ mirroring: tells the rbd-mirror daemon to replicate images
● Images have states: primary and non-primary (promote and demote calls)
● 1:1 relationship between daemons but cross-replication possible

RBD Mirroring - Ceph Luminous
Ceph Luminous release
(Aug 2017, current):
● RBD-Mirror, multiple instances
with failover
● Only a single instance is
active
● Multiple secondary sites
(unidirectional)
● Delayed replication (for
unwanted change)

RBD Mirroring - Ceph Mimic
Ceph Mimic release (rc1 May 2018):
● RBD-Mirror, multiple active
instances
● ‘Simple’ algorithm for chunking
● Naive chunking policy, divides m
daemons and n images in a way
● Dashboard V2 mirroring
integration
● Delayed deletion
● Clone non-primary images (for
Glance)

Disaster Recovery with RBD Mirroring
EASIER WAYS SAFEGUARD DATA IN OPENSTACK DEPLOYMENTS
TripleO
ceph-ansible
CLUSTER ONE DR1
BLOCKBLOCK
rbd-mirror
images
data
OS
images
data
OS
RBD MIRRORING DEPLOYED WITH TRIPLEO

Cinder Replication w/RBD Mirroring

Cinder RBD Replication
● New in Queens release: Tripleo
deployment of RBD-mirror daemon
using ceph-ansible
● Replication is enabled per-volume
● Cinder assumes Ceph cluster
mirroring is configured and
functioning
● Underlying configuration can
mirror to multiple sites, cinder can
be configured to reflect this
configuration and allow multiple
failover targets
● Failover changes cinder runtime
configuration and promotes each
volume to the secondary.
● Upcoming feature to promote a
secondary to primary
● A/A replication in RBD merged this
cycle

Cinder Replication Failover / Promote
What’s available today?
● Ocata release - RBD Cinder Volume Replication driver
○ Volume based added rather than just pool level (based on Cinder Volume Types)
○ Both clusters are expected to be
configured with rbd-mirror with keys in place and image mirroring
enabled on the pool.
○ The RBD driver will enable replication per-volume if the volume type requests it.
○ Supports Multiple mirroring clusters
● After failing backend A over to backend B, there is was no mechanism in Cinder to promote
backend B to the master backend in order to then replicate to a backend C. We also lacked some
management commands to help rebuild after a disaster if states get out of sync.

Cinder Replication Promotion Failback
● Add support for promoting a failed over backend
○ Cinder's failover support allows us to test a disaster recovery configuration by
initiating a failover operation and verifying that the driver correctly passes
control of the replicated volumes to a secondary site.
○ With the recent merge of the RBD replication in the Cinder driver, this failover
is now supported for ceph-backed cinder deployments.
○ Cinder also provides a failback operation to allow an administrator to undo a
previous failover.
Rocky Release focus

Cinder Replication Promotion Failback
● Add support for Active/Active replication in Cinder RBD driver
○ This allows you to configure multiple volume backends that are all a member
of the same cluster participating in replication.
○ The new feature breaks failover_host into the two requisite parts (Failover
and Failover_completed) in order to support both single-backend and
multiple backends configured as active/active.
Rocky Release focus

Cinder RBD Replication
Gaps
● Nova attached volumes are no longer connected
● Cannot replicate a multi-attach volume or multi-attach a
replicated volume
● No “gate testing” yet if the promotion works

Use your RBD Backups for DR

Cinder RBD Backup with RBD Mirroring
When something goes wrong:
● Re-configure Cinder Backup to point to the mirrored cluster
● Force detach the volume
● Restore the backup to a new volume
● Attach the volume again to the virtual machine
○ If boot from volume:
■ Reset-state (should be in failed state)
■ Start the virtual machine again
● Best Practice - use Export and import backup metadata
○ Exporting and storing this encoded string metadata allows you to completely restore the
backup, even in the event of a catastrophic database failure.
■ $ cinder backup-export BACKUP_ID
■ $ cinder backup-import METADATA
Ceph Cinder Backup recovery procedure

Protecting the Edge

● Edge sites hosting content for
low-latency delivery
● Remote POPs running virtual
network functions
● Micro data centers capturing
IOT telemetry fo real-time
processing
Micro Data
Center
Edge
CDN
Primary Data Center
Remote
POP
(NFV)
Remote
POP
(NFV)
Edge
CDN
Edge
CDN
Micro Data
Center
Protecting the Edge
Compute and Storage supporting key Apps at the edge

Distributed NFVi
Protecting Virtual Network Functions at the Edge
Source: Brian Lavallée @ Ciena

Distributed Compute Nodes architecture
RS1: 10 compute nodes RS2: 10 compute nodes RSX: 14 compute nodes
Distributed Compute
Controller nodes
Compute and Storage nodes
RS = Remote Site

Distributed Compute Nodes with Ceph
● To ensure performance, Ceph storage nodes need to communicate with Computes on
a low latency and high bandwidth network.
● What means Ceph storage nodes are collocated with the computes on the same Local
Area Network (LAN) in an Hyper-Converged manner.
● In Distributed NFV, Ceph storage is used as a back-end for:
○ Nova: stateless VNF’s requires ephemeral storage on Ceph
○ Cinder: statefull VNF’s requires persistent storage use Cinder volumes
○ Glance: use Ceph in the Compute zone as a backend to spawn VNFs quickly (as
you do not want to rely on image transfer delay between 2 remote sites)
○ Leverage Ceph “copy on write” to speed-up the spawing process.

Protecting Images the Edge
● Distributed NFV use case also requires to support multi-backend (multiple Ceph
clusters) for Glance , where the image is uploaded once and replicated on all the POPs
using Ceph.
● With Ceph storage nodes in each compute zone, without having to use additional
physical servers for the control plane, one solution being to support the collocation of
Ceph MON and Ceph OSD on the same physical servers .
● Benefits
○ Reduces hardware footprint since we have a centralized control plane
○ Brings the ability to manager multiple Ceph cluster from the centralized control
plane
○ Brings resilience with multiple AZs

● Using a third party proxy
○ Project MixMatch
■ Combines resources across federated OpenStack deployments
■ The Proxy Service will forward REST API requests to a remote service
provider which is federated using Keystone-to-Keystone Federation (K2K).
■ The proxy learns the location of resources and is able to forward requests
to the correct service provider.
■ This allows OpenStack services to use resources provided by other
federated OpenStack deployments, ex. Nova attach a remote volume.

Introducing Glance Multi-backend - Rocky release work in progress
● Ability to store Glance images in different storage backends
● Multi-store support opens the door to a handful of image replication and backend targeting use
cases which can provide additional value related to fault tolerance, image locality and policy
based image hosting.
● Allowing Glance Metadata to manage the location awareness in a the centralized control plane,
where store drivers need to express the different storage backends.
● Support multiple Ceph clusters (one per backend) where one backend will represent a
distributed site
● Allow to specify specific Glance backend at the edge - for example CDN specific image.
● Glance does not need to deal with how to sync images between clusters, rather than add the
store logic to support it.
● Additional work needed in Stein release for Store drivers to interact with Glance.

Object Replication

Ceph Rados Gateway (RGW)
RGW Multisite replication (Global Clusters)
● Global object storage clusters with a single namespace
● Enables deployment of clusters across multiple locations
● Locally immediately consistent, remote eventually consistent
● Clusters synchronize
○ allowing users to read from or write to the closest one
● Active-active replication
○ Metadata operations reserved for the master

Where we going?

• “archive”
• Time-based
• Manual retrieval
Roadmap: Ceph Rados Gateway sync to S3
Ability to sync Ceph Rados Gateway private object store to public S3 Cloud providers (e.g:
Amazon S3).
● Tiering to cloud
● Tiering to tape
• “Cloudsync”
• No policy support
Mimic
May 2018
Future • Tiering
• Heat-based data migration
• Migrate back on access
Nautilus
H1 2019

Roadmap: RBD Mirror
Ability to asynchronously synchronize volume images across multiple Ceph clusters
● Streaming changes live to a secondary site (DR)
● Volumes are ready to consume and can be immediately be pressed into production
• active/passive HA
• Triple-O support
• 1:many replication
Luminous
August 2017
• Adaptive balancingMimic
May 2018
• active/active HA
• scale-out
• Naive balancing
Future

Plan Before the Meltdown

Putting it all together
● Cloud Meltdown A3 (can happen anywhere to anyone, anytime)
● The Good news, it is preventable (different failure domains from snaps and backups
combined with block and object replication)
● The secret: Design you Apps with HA. Architect OpenStack and Ceph properly.
● Distribute your data using the latest Cinder Replication with Ceph block and object
replication
● Extend your RBD Backups for DR using Ceph replication
● Use Ceph to to protect your Edge footprint by leveraging Ceph/Glance multi-backend
support
● Automate and test it!
● Next Cloud Meltdown your cloud users may hardly even notice...

0xF2
leseb_
SeanCohen_RH
THANK YOU

Backup slides
(bwahahaha)

Backups - If your cluster is gone
Controller-node
config file
backup
config
volume
config
cinder-api
AMQP
cinder backup
RBD backup
drivercinder volume
volume driver
code
Procedure to resume activity:
● Force detach volumes from instances
● Reconnect all OpenStack services to consume
the backup cluster (Glance, Nova, Cinder)
● Restart them
● Re-attach volumes to your instances
Resume activity, rebuild the initial cluster and sync
back everything with rbd-mirroring.

RBD Mirroring Setup
● Use symlinks to point to other cluster configuration
● Routable connectivity between sites
● Deploy the rbd-mirror daemon on each cluster
● Same pools configuration
● Add peering pool
● Add RBD image settings
○ Enable journaling on image
○ Mirror pool or specific images
Considerations:
● LibRBD-only, no current kRBD support
● Bluestore and EC pool for block (multiple pools, mirror only EC pool, leave metadata pool alone)

How to Survive an OpenStack Cloud Meltdown with Ceph

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