Skip to main content
NetApp Knowledge Base

VAAI: How does caching work with FlexGroups?

Views:
153
Visibility:
Public
Votes:
2
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

 

 

NetApp provides no representations or warranties regarding the accuracy or reliability or serviceability of any information or recommendations provided in this publication or with respect to any results that may be obtained by the use of the information or observance of any recommendations provided herein. The information in this document is distributed AS IS and the use of this information or the implementation of any recommendations or techniques herein is a customer's responsibility and depends on the customer's ability to evaluate and integrate them into the customer's operational environment. This document and the information contained herein may be used solely in connection with the NetApp products discussed in this document.