.. _ceph-guide: ============= Ceph in Kolla ============= The out-of-the-box Ceph deployment requires 3 hosts with at least one block device on each host that can be dedicated for sole use by Ceph. However, with tweaks to the Ceph cluster you can deploy a **healthy** cluster with a single host and a single block device. Requirements ============ * A minimum of 3 hosts for a vanilla deploy * A minimum of 1 block device per host Preparation =========== To prepare a disk for use as a `Ceph OSD `_ you must add a special partition label to the disk. This partition label is how Kolla detects the disks to format and bootstrap. Any disk with a matching partition label will be reformatted so use caution. To prepare an OSD as a storage drive, execute the following operations: :: # # where $DISK is /dev/sdb or something similar parted $DISK -s -- mklabel gpt mkpart KOLLA_CEPH_OSD_BOOTSTRAP 1 -1 The following shows an example of using parted to configure ``/dev/sdb`` for usage with Kolla. :: parted /dev/sdb -s -- mklabel gpt mkpart KOLLA_CEPH_OSD_BOOTSTRAP 1 -1 parted /dev/sdb print Model: VMware, VMware Virtual S (scsi) Disk /dev/sdb: 10.7GB Sector size (logical/physical): 512B/512B Partition Table: gpt Number Start End Size File system Name Flags 1 1049kB 10.7GB 10.7GB KOLLA_CEPH_OSD_BOOTSTRAP Using an external journal drive ------------------------------- The steps documented above created a journal partition of 5 GByte and a data partition with the remaining storage capacity on the same tagged drive. It is a common practice to place the journal of an OSD on a separate journal drive. This section documents how to use an external journal drive. Prepare the storage drive in the same way as documented above: :: # # where $DISK is /dev/sdb or something similar parted $DISK -s -- mklabel gpt mkpart KOLLA_CEPH_OSD_BOOTSTRAP_FOO 1 -1 To prepare the journal external drive execute the following command: :: # # where $DISK is /dev/sdc or something similar parted $DISK -s -- mklabel gpt mkpart KOLLA_CEPH_OSD_BOOTSTRAP_FOO_J 1 -1 .. note:: Use different suffixes (``_42``, ``_FOO``, ``_FOO42``, ..) to use different external journal drives for different storage drives. One external journal drive can only be used for one storage drive. .. note:: The partition labels ``KOLLA_CEPH_OSD_BOOTSTRAP`` and ``KOLLA_CEPH_OSD_BOOTSTRAP_J`` are not working when using external journal drives. It is required to use suffixes (``_42``, ``_FOO``, ``_FOO42``, ..). If you want to setup only one storage drive with one external journal drive it is also necessary to use a suffix. Configuration ============= Edit the [storage] group in the inventory which contains the hostname of the hosts that have the block devices you have prepped as shown above. :: [storage] controller compute1 Enable Ceph in ``/etc/kolla/globals.yml``: :: enable_ceph: "yes" RadosGW is optional, enable it in ``/etc/kolla/globals.yml``: :: enable_ceph_rgw: "yes" RGW requires a healthy cluster in order to be successfully deployed. On initial start up, RGW will create several pools. The first pool should be in an operational state to proceed with the second one, and so on. So, in the case of an **all-in-one** deployment, it is necessary to change the default number of copies for the pools before deployment. Modify the file ``/etc/kolla/config/ceph.conf`` and add the contents:: [global] osd pool default size = 1 osd pool default min size = 1 Deployment ========== Finally deploy the Ceph-enabled OpenStack: :: kolla-ansible deploy -i path/to/inventory Using a Cache Tier ================== An optional `cache tier `_ can be deployed by formatting at least one cache device and enabling cache. tiering in the globals.yml configuration file. To prepare an OSD as a cache device, execute the following operations: :: # # where $DISK is /dev/sdb or something similar parted $DISK -s -- mklabel gpt mkpart KOLLA_CEPH_OSD_CACHE_BOOTSTRAP 1 -1 Enable the Ceph cache tier in ``/etc/kolla/globals.yml``: :: enable_ceph: "yes" ceph_enable_cache: "yes" # Valid options are [ forward, none, writeback ] ceph_cache_mode: "writeback" After this run the playbooks as you normally would. For example: :: kolla-ansible deploy -i path/to/inventory Setting up an Erasure Coded Pool ================================ `Erasure code `_ is the new big thing from Ceph. Kolla has the ability to setup your Ceph pools as erasure coded pools. Due to technical limitations with Ceph, using erasure coded pools as OpenStack uses them requires a cache tier. Additionally, you must make the choice to use an erasure coded pool or a replicated pool (the default) when you initially deploy. You cannot change this without completely removing the pool and recreating it. To enable erasure coded pools add the following options to your ``/etc/kolla/globals.yml`` configuration file: :: # A requirement for using the erasure-coded pools is you must setup a cache tier # Valid options are [ erasure, replicated ] ceph_pool_type: "erasure" # Optionally, you can change the profile #ceph_erasure_profile: "k=4 m=2 ruleset-failure-domain=host" Managing Ceph ============= Check the Ceph status for more diagnostic information. The sample output below indicates a healthy cluster: :: docker exec ceph_mon ceph -s cluster 5fba2fbc-551d-11e5-a8ce-01ef4c5cf93c health HEALTH_OK monmap e1: 1 mons at {controller=10.0.0.128:6789/0} election epoch 2, quorum 0 controller osdmap e18: 2 osds: 2 up, 2 in pgmap v27: 64 pgs, 1 pools, 0 bytes data, 0 objects 68676 kB used, 20390 MB / 20457 MB avail 64 active+clean If Ceph is run in an **all-in-one** deployment or with less than three storage nodes, further configuration is required. It is necessary to change the default number of copies for the pool. The following example demonstrates how to change the number of copies for the pool to 1: :: docker exec ceph_mon ceph osd pool set rbd size 1 All the pools must be modified if Glance, Nova, and Cinder have been deployed. An example of modifying the pools to have 2 copies: :: for p in images vms volumes backups; do docker exec ceph_mon ceph osd pool set ${p} size 2; done If using a cache tier, these changes must be made as well: :: for p in images vms volumes backups; do docker exec ceph_mon ceph osd pool set ${p}-cache size 2; done The default pool Ceph creates is named **rbd**. It is safe to remove this pool: :: docker exec ceph_mon ceph osd pool delete rbd rbd --yes-i-really-really-mean-it Troubleshooting =============== Deploy fails with 'Fetching Ceph keyrings ... No JSON object could be decoded' ------------------------------------------------------------------------------ If an initial deploy of Ceph fails, perhaps due to improper configuration or similar, the cluster will be partially formed and will need to be reset for a successful deploy. In order to do this the operator should remove the `ceph_mon_config` volume from each Ceph monitor node: :: ansible \ -i ansible/inventory/multinode \ -a 'docker volume rm ceph_mon_config' \ ceph-mon ===================== Simple 3 Node Example ===================== This example will show how to deploy Ceph in a very simple setup using 3 storage nodes. 2 of those nodes (kolla1 and kolla2) will also provide other services like control, network, compute, and monitoring. The 3rd (kolla3) node will only act as a storage node. This example will only focus on the Ceph aspect of the deployment and assumes that you can already deploy a fully functional environment using 2 nodes that does not employ Ceph yet. So we will be adding to the existing multinode inventory file you already have. Each of the 3 nodes are assumed to have two disk, ``/dev/sda`` (40GB) and ``/dev/sdb`` (10GB). Size is not all that important... but for now make sure each sdb disk are of the same size and are at least 10GB. This example will use a single disk (/dev/sdb) for both Ceph data and journal. It will not implement caching. Here is the top part of the multinode inventory file used in the example environment before adding the 3rd node for Ceph: :: [control] # These hostname must be resolvable from your deployment host kolla1.ducourrier.com kolla2.ducourrier.com [network] kolla1.ducourrier.com kolla2.ducourrier.com [compute] kolla1.ducourrier.com kolla2.ducourrier.com [monitoring] kolla1.ducourrier.com kolla2.ducourrier.com [storage] kolla1.ducourrier.com kolla2.ducourrier.com Configuration ============= To prepare the 2nd disk (/dev/sdb) of each nodes for use by Ceph you will need to add a partition label to it as shown below: :: # parted /dev/sdb -s -- mklabel gpt mkpart KOLLA_CEPH_OSD_BOOTSTRAP 1 -1 Make sure to run this command on each of the 3 nodes or the deployment will fail. Next, edit the multinode inventory file and make sure the 3 nodes are listed under [storage]. In this example I will add kolla3.ducourrier.com to the existing inventory file: :: [control] # These hostname must be resolvable from your deployment host kolla1.ducourrier.com kolla2.ducourrier.com [network] kolla1.ducourrier.com kolla2.ducourrier.com [compute] kolla1.ducourrier.com kolla2.ducourrier.com [monitoring] kolla1.ducourrier.com kolla2.ducourrier.com [storage] kolla1.ducourrier.com kolla2.ducourrier.com kolla3.ducourrier.com It is now time to enable Ceph in the environment by editing the ``/etc/kolla/globals.yml`` file: :: enable_ceph: "yes" enable_ceph_rgw: "yes" enable_cinder: "yes" glance_backend_file: "no" glance_backend_ceph: "yes" Finally deploy the Ceph-enabled configuration: :: kolla-ansible deploy -i path/to/inventory-file