VAAI: How does caching work with FlexGroups?
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- Category:
- netapp-nfs-plug-in-for-vmware-vaai
- Specialty:
- virt
- Last Updated:
Applies to
- NFS
- Flexgroup Volumes
- VMware VAAI (vSphere APIs for Array Integration)
Answer
NetApp Flexgroup volumes offer VAAI support for the Full File Clone primitive. To enable support for VAAI and flexgroup volumes, please see https://kb.netapp.com/onprem/ontap/dm/VAAI/How_to_Configure_ONTAP_FlexGroups_to_allow_VAAI_copy_offload.
When reviewing FlexGroup volumes copy-offload options, there are options that pertain to template caching. This article will explain template caching and what behavior these options will change:
::*> vserver copy-offload show
FG FG
FG Optimized Optimized
Subfile- Avoid Optimized Copy Cache Copy Cache QoS
Vserver NFS SCSI Sisclone Punching Copy Autodelete Timeout Throttle
------- ----- ----- -------- -------- --------- ---------- ---------- --------
svm1
enabled
enabled
enabled disabled disabled on 160 0B
Template Caching
When performing clones on a datastore using FlexGroup volumes:
- initial clones are slower than in a FlexVol datastore initially
- this is because the Flexgroup volumes must first populate it's template cache
- subsequent clones, once the template cache is populated, will have performance on par with FlexVol datastores.
Flexgroup optimized copy cache autodelete / Flexgroup optimized Copy Cache Timeout
- "Flexgroup optimized copy cache autodelete" is used to to control the auto-deletion of the cache copy by ONTAP
- Auto-deletion runs every 20 minutes and looks for cached data that has exceeded the "Flexgroup optimized Copy Cache Timeout". This value is in minutes.
- Setting "Flexgroup optimized Copy Cache Timeout" to zero does not disable the timeout. Instead, this will immediately mark the cache entry for deletion.
- Everytime you use a cached copy, the cache timeout for the copy is reset.
- To keep the cache copy, disable "Flexgroup optimized copy cach autodelete" by running:
vserver copy-offload modify -flexgroup-optimized-copy-cache-autodelete off
- Deleting the cache copy is not allowed by admin user. This auto deletion is managed by ONTAP if "FG Optimized Copy is enabled"
- If a clone's source file is updated before the cache timeout:
- all cache copies will be invalidated
- a new cache copy is prepared on all the constituent volumes where the VM clones will be placed
- When cache copies have been idle and if the "Flexgroup optimized Copy Cache Timeout" is satisfied, than ONTAP will perform a cleanup
Additional Information