Ceph with CloudStack

Andrija Panic™
Cloud Architect
andrija.panic@shapeblue.com
Twitter: @AndrijaRS
Ceph with CloudStack
The Cloud Specialists

• Cloud Architect @ ShapeBlue
• From Belgrade, Serbia
• Committer and PMC member
• Involved with CloudStack since version 4.0.0-incubating
• Interested in:
• Cloud infrastructure architecture and engineering.
• Virtualization, Storage and SDxx
• Downtime:
• Father to 2 princesses
• Music, gym and hobby electronic

“The name Ceph comes from cephalopod, a class of molluscs that
includes the octopus and squid… the reasoning had something to
do with their high level of intelligence and “many-tentacled”,
“distributed” physiology.”
Sage Weil
Fun facts:
• Cephalopods have the most complex nervous system of all the invertebrates.
• Some can fly up to 50m through the air, squirting water to help propel themselves.
• Most have special coloured pigments on their skin that are used for camouflage.
• Cephalopods have advanced vision, but most are colour blind.
• They have an ink sac that they squirt into the water to confuse predators

• Open source SDS solution
• Highly scalable (tens of thousands of nodes)
• No single point of failure
• Hardware agnostic, “runs on commodity hardware”
• Self-managed whenever possible
• Built around the CRUSH algorithm
• Provides multiple access methods:
• File
• Block
• Object (S3/Swift)
• NFS gateway (third-party sw.) for backward compatibility

• The Ceph Storage Cluster (RADOS cluster) is the foundation for all
Ceph deployments.
• Based upon RADOS, consists of three types of daemons:
• Ceph Object Storage Daemon (OSD)
• Ceph Monitor (MON)
• Ceph Meta Data Server (MDS) - optionally
• A minimal possible system will have at least one Ceph Monitor
and two Ceph OSD Daemons for data replication.
• Production system will have at least 3 monitors (redundancy) and
minimum 10 OSD nodes (i.e. 80+ OSDs)

Ceph Storage Cluster (RADOS cluster)
• OSD and MON are mandatory for every cluster
• MDS is required only if using Ceph FS
OSDs:
• 10s to 10000s in a cluster, one per disk (HDD, SSD, NVME)
• Serve stored objects to clients
• Intelligently peer to perform replication/recovery tasks
MONs:
• Maintain a master copy of the Ceph cluster map,
cluster membership and state
• Provide consensus for distributed decision-making
via PAXOS algorithm
• Small, odd number, do not serve objects to clients

Preparation
• Make sure the time across all servers is synced with less then 0.05sec of difference!
(don’t worry, Ceph will complain if not synced)
• Make sure that “hostname --fqdn” is resolvable between all nodes
• Make sure key-based ssh auth from admin node to all cluster nodes is working (sudo)
• Add proper release repo on the “admin” node, install “ceph-deploy”

Installation (using ceph-deploy from the admin node)
• mkdir mycluster; cd mycluster;
• ceph-deploy new ceph-node1 ceph-node2 ceph-node3 (make cluster def.)
• ceph-deploy install --release nautilus ceph-node1 ceph-node2 ceph-node3 (install binaries only)
• ceph-deploy mon create-initial (create MONs across initially added Ceph nodes)
• ceph-deploy admin ceph-node1 ceph-node2 ceph-node3 (copy ceph.conf and the needed keyrings)
• for n in 1 2 3; do ceph-deploy osd create --data /dev/sdb ceph-node$n; done (deploy single OSD per node)
Ceph dashboard (optional but recommended)
• yum install -y ceph-mgr-dashboard
• ceph config set mgr mgr/dashboard/ssl false
• ceph mgr module enable dashboard
• ceph dashboard ac-user-create admin password administrator

Create a pool for CloudStack
• ceph osd pool create cloudstack 64 replicated
• ceph osd pool set cloudstack size 3
• rbd pool init cloudstack
• ceph auth get-or-create client.cloudstack mon 'profile rbd' osd 'profile rbd pool=cloudstack’*
Example key:
[client.cloudstack]
key = AQAb6M9cY1epJBAAZgzlOlpZSpBcUpYCBWTFrA==
Configure write-back caching on KVM nodes (setup ssh/name resolution from the admin node)
• cat << EOM >> /root/mycluster/ceph.conf
[client]
rbd cache = true
rbd cache writethrough until flush = true
EOM
• ceph-deploy --overwrite-conf admin kvm1 kvm2 kvm3

View/Manage OSDs
Manage basic cluster configs

View/Manage pools
View/Manage RBD images

New in Nautilus (based on SUSE’s OpenATTIC mostly)
• OSD management (mark as down/out, change OSD settings, recovery profiles)
• Cluster config settings editor
• Ceph Pool management (create/modify/delete)
• ECP management
• RBD mirroring configuration
• Embedded Grafana Dashboards (derived from Ceph Metrics)
• CRUSH map viewer
• NFS Ganesha management
• iSCSI target management (via ceph-iscsi)
• RBD QoS configuration
• Ceph Manager (ceph-mgr) module management
• Prometheus alert Management
• Support for multiple users / roles; SSO (SAMLv2) for user authentication

(Some) Nautilus improvements:
• pg_num can be reduced; can be auto-tuned in the background
• OSD and mon report SMART stats; Failure prediction; Optional automatic migration*
• Mon protocol v2, port 6789 → 3300 (IANA); encryption; dual (v1 and v2) support
• osd_target_memory; NUMA mgmt & OSD pinning; misplaced no more HEALHT_WARN
• S3 tiering policy, bucket versioning
• RBD live image migration (librbd only); rbd-mirror got simpler; rbd top & and rbd CLI;
• CephFS multi-fs support stable; Clustered nfs-ganesha (active/active)
• Run Ceph clusters in Kubernetes (Rook, ceph-ansible)

Add Ceph to CloudStack Create offerings for Ceph
- Deploy a VM

Let’s check our ACS volume on Ceph

Volume provisioning steps:
• Copy template from SS to Ceph: “0a7cd56c-beb0-11e9-b920-1e00c701074a”
• Create a base snapshots and protect it (can’t be deleted): “cloudstack-base-snap”
• Create a VM’s volume as the child (clone) of the snap: “feb056c5-72d4-400a-92c2-f25c64fe9d26”
Find all volumes (children) of specific template (base-snap of the template image)
<root@ceph1># rbd children cloudstack/0a7cd56c-beb0-11e9-b920-1e00c701074a@cloudstack- base-snap
cloudstack/feb056c5-72d4-400a-92c2-f25c64fe9d26
cloudstack/8481fcb1-a91e-4955-a7fc-dd04a44edce5
cloudstack/9b8f978b-74d0-48f7-93f6-5e06b9eb6fd3
cloudstack/3f65da05-268f-41fa-99b2-ce5d4e6d6597
…

Manually reproducing the ACS behavior:
rbd create -p cloudstack mytemplate --size 100GB (or “qemu-img” convert, or “rbd import”…)
rbd snap create cloudstack/mytemplate@cloudstack-base-snap
rbd snap protect cloudstack/mytemplate@cloudstack-base-snap
rbd clone cloudstack/mytemplate@cloudstack-base-snap cloudstack/myVMvolume
…and the cleanup:
[root@ceph1 ~]# rbd rm cloudstack/myVMvolume
Removing image: 100% complete...done.
[root@ceph1 ~]# rbd snap unprotect cloudstack/mytemplate@cloudstack-base-snap
[root@ceph1 ~]# rbd snap rm cloudstack/mytemplate@cloudstack-base-snap
Removing snap: 100% complete...done.
[root@ceph1 ~]# rbd rm cloudstack/mytemplate
Removing image: 100% complete...done.

“Hacking” the customer’s volume:
• rbd map myPool/myImage (kernel client)
(will usually fail due to kernel client “rbd.ko” being way behind the cluster version/capabilities)
• rbd-nbd map myPool/myImage (user-space, via librbd)
(requires “yum install rbd-nbd” and “modprobe nbd max_part=15*”)
• qemu-nbd --connect=/dev/nbd0 rbd:myPool/myImage (user-space, via librbd)
(requires “modprobe nbd*”)
Qemu-img:
• qemu-img info rbd:cloudstack/47b1cfe5-6bab-4506-87b6-d85b77d9b69c*
• qemu-img info rbd:cloudstack/47b1cfe5-6bab-4506-87b6-
d85b77d9b69c:mon_host=10.x.x.y:auth_supported=Cephx:id=cloudstack:key=AQAFSZ……..jEtr/g==

• No support for a full VM snapshot (technically not possible with Ceph/iSCSI/raw block devices)
• No support for the storage heartbeat file (yet…)
• Currently not possible to really restore a volume from a snapshot (old behaviour stays*)
• Two “external” libraries to be aware of – librbd and rados-java

Not your average NFS:
• Ceph can be a rather complex storage system to comprehend
• Make sure you know the storage system well before relying on it in production
• Make sure to excel at troubleshooting, you’ll need it sooner or later
• Understand how the things works under the hood
• Understand recovery throttling to avoid high impact on customer IO

• “Works on commodity hardware”, but don’t expect miracles
• Writing data to primary OSD and replicating that write to another 2 OSDs, takes time
• Latency is very good with NVME (0.5ms-1ms)
• Not so very good with HDD/SSD mix (10ms-30ms)
• Never, ever, ever… use consumer SSDs; bench and test specific enterprise SSD models
• Too many parallel stream end up generating pure random IO pattern on the backend
• Ceph was (unofficially) considered unsuitable for serious random IO workload (2-3y ago)*

Things have seriously changed last few years (especially with the new BlueStore backend)
• Writing to the raw device (“block”) vs. XFS on FileStore;
• RockDB (“block.db”, “block.wal”) vs. LevelDB
• Now suitable for pure SSD/NVME clusters
• Increased throughput 40-300%*, reduced latency 30-50%* vs. FileStore
• Explicit memory management* (BlueStore runs in user-space)
• Data and metadata checksums; Compression
• Reads still served from Primary OSD only 

Step by step guide for Ceph with CloudStack (Mimic):
• https://www.shapeblue.com/ceph-and-cloudstack-part-1/

CloudStack
ShapeBlue.com • @ShapeBlue
An d r i j a P a n i c , C l o u d a r c h i t e c t • P M C Ap a c h e C l o u d S t a c k
a n d r i j a . p a n i c @ s h a p e b l u e . c o m • @ An d r i j a R S

Ceph with CloudStack

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