OpenStack Cinder

An Overview

Created by Jon Bernard

In A Nutshell

First class block storage

Independent lifespan

Integrates enterprise storage platforms

Architecture

Interactions

• Nova
• Glance
• Keystone

Requirements

• AMQP
• MySQL
• Python (+ libraries)
• Storage Backend

Functionality

• Volume
• Snapshot
• Backup
• Transfer
• Migrate
• Type
• Quota
• QOS

Configuration

/etc/cinder/cinder.conf

Debugging

[DEFAULT]
verbose = True  # useful information
debug = True    # something like a firehose

• Logs are found in /var/log/cinder
• Look for words like "ERROR" and "Exception"
• If you see a stacktrace in the logs, that's bad
• The cinder client accepts --debug

Previous Features

• Disk Encryption
• Volume Migration
• Volume Rate Limiting
• Volume Extension
• Transfer Volume Ownership
• Scheduler Hints

Disk Encryption

• Handled by Nova, Cinder remains unchanged
• Reference implementation uses dm-crypt
• Other volume encryptors can be substituted
• See the wiki page for more details.

Volume Migration

• Migrate a volume from one backend to another
• Live, not visible by the instance

  $ cinder migrate <volume> <target>

Volume Rate Limiting

• Allows I/O rate limiting per volume
• Separate read and write limits
• Enforced in Nova or Cinder driver

Volume Extension

• Increase size of an existing volume
• iSCSI target is not updated (bug)

Transfer Ownership

Transfer a volume from one tenant to another

cinder transfer-create <volume>                 # tenant A
cinder transfer-accept <transfer_id> <auth_key> # tenant B

Scheduler Hints

• User can pass hints to volume create
• Scheduler uses hints at volume-create time
• API v2 only
• Blueprint is here

New Features

• Volume import/export
• Complete i18n enablement *
• Limit volume copy bandwith
• Include image-creation proprties *
• Volume number scheduler
• Consistency groups
• Pool-Aware scheduling
• Backup quotas *
• Volume replication *

Volume Import/Export

• Import volumes from other environments
• Export is a bit unintuitive
• Export releases a volume from cinder
• Similiar to delete operation
• Data on underlying volume untouched

Limit Volume Copy Bandwith

• New volume from image
• Volume backup
• Volume deletion (scrub)
• ionice doesn't always work
• uses blkio cgroup for throttling
• falls short when volume isn't a file on disk

Consistency Groups

• Volume Container
• Assign volume at creation time
• Perform operations on the group (snapshot, backup, etc)
• Cinder quiesces volumes through nova

Pool-Aware Scheduling

• Finer granularity than backend, sub-pools
• Volume or snapshot that is larger than pool fails
• Capacity reporting that makes sense

Upcoming Features

• Many driver-specific improvements
• Cinder objects *
• Backup encrypted volumes
• Incremental backup
• Modify existing consistency group
• Volume migration for Ceph/RBD
• Private volumes
• Over subscription in thin backends

Cinder Objects

• Bundle data with methods that can operate on them
• service, volume, type, snapshot, quota, backup, and CG
• Isolates the code from the DB schema
• Eaiser rolling upgrades
• Objects can passed over RPC and data lazy-loaded from DB

Questions?