8ca13afc49
This will now require a separate section "Use Cases". This was originally within "Problem description", but use cases seems to be missed when it was filled out. This will hopefully improve spec submission. Change-Id: I3615ca5ff5c46851e682739a8343242e2f1b0a8d
3.0 KiB
Limit Bandwidth of Volume Copy
Include the URL of your launchpad blueprint:
https://blueprints.launchpad.net/cinder/+spec/limit-volume-copy-bandwidth
This proposes adding a new config to limit bandwidth for volume copy to mitigate interference to other instance performance during:
- new volume creation from a image
- backup
- volume deletion (when dd if=/dev/zero etc. is chosen to wipe)
Problem description
Currently, volume copy operations consumes disk I/O bandwidth heavily and may slow down the other guest instances.
"ionice" option is already implemented in some cases, but it is not always usable. e.g. When instances directly access to the storage and doesn't go through I/O scheduler of cinder control node, ionice cannot control I/O priority and instances access may slow down.
Use Cases
Proposed change
A new config named 'volume_copy_bps_limit' will be added to determine max bandwidth (byte per second) consumed by volume copy.
When CONF.volume_copy_bps_limit is zero (default), no limitation is applied, and no cgroup is created.
Otherwise, bandwidth limitation is applied to volume copy. For example, if the volume copy is done by 'dd' command, it can be implemented by putting 'dd' into blkio cgroup for throttling.
Alternatives
When volume copy commands have an option for I/O throttling, the usage of such options are preferable. Putting whole cinder-volume processes into blkio cgroups could also be a solution for this, though it is required to provide a way to set rate limit to newly added block devices when new volume is created.
Data model impact
None
REST API impact
None
Security impact
None
Notifications impact
None
Other end user impact
None
Performance Impact
When volume copy I/O bandwidth is limited, it takes more time to complete volume copy. Users are required to balance between volume copy performance and interference to instances performance.
Other deployer impact
- This feature is disabled by default. Users who want to use this feature need to set 'volume_copy_bps_limit' in cinder.conf.
Developer impact
None
Implementation
Assignee(s)
- Primary assignee:
-
tomoki-sekiyama-g
Work Items
- Implement cgroup blkio setup functions
- Implement I/O rate limit for volume_utils.copy_volume
- Implement I/O rate limit for other image format such as qcow
Dependencies
None
Testing
None
Documentation Impact
The cinder client documentation will need to be updated to reflect the new config.
References
None