EUC Tip 94: Dedupe your base image with no performance overhead. #Xen #View #RDS

Nutanix uses a scaling approach for sizing the Controller Virtual Machine (CVM) that lives on each node/server in the cluster. 8 GB of RAM is reserved for services like Zeus(config data), Medusa(Metadata), Prism(UI), Cluster Health and Cerebro (DR). Pretty efficient considering all the enterprise features the CVM is delivering. The remaining RAM is used for Stargate which is responsible for servicing IO requests. Of the remaining RAM 40% is used for the extent cache and content cache (Deduped cache).

How Nutanix scales the local cache for dedupe and non-deduped data in NOS 3.5

How Nutanix scales the local cache for dedupe and non-deduped data in NOS 3.5

Stargate RAM = CVM RAM – 8G (typically)
Total Available For Cache = 40% of Stargate RAM
Extent Cache = 60% of Total Cache (typically; but we give at least 4G when possible).
Content Cache = Total Cache – Extent Cache (but min of 1G; otherwise off)

You can see when sizing the CVM between 20 – 24 GB the extent cache stays static. If you have a workload that not using VAAI like using MCS, view composer(non-VCAI) or RDS with the applications built into the base image you can take advantage of the content cache without any overhead of inline dedupe. My simply doing a manual fingerprint(SHA1) of the golden image you can utilize this space. This will save lots of space in the content cache and ensure the most used bits never leave your overall cache even in the advent of a really nasty anti-virus problem.

To manual fingerprint the base image you can log into anyone of the CVM’s and run this command:

nutanix@cvm$ vdisk_manipulator --operation="add_fingerprints" --nfs_container_name="ctr_name" --relative_file_path="vdisk_path"

Replace ctr_name with the name of the container where the vDisk to fingerprint resides.
Replace vdisk_path with the path of the vDisk to fingerprint relative to the container path (for example, Win7-desktop/Win7-desktop.vmdk).


  1. Nishant Dhingra says:

    Hi the command mentioned:

    nutanix@cvm$ vdisk_manipulator –operation=”add_fingerprints” –nfs_container_name=”ctr_name” –relative_file_path=”vdisk_path”

    This is incorrect: It is not relative_file_path, it is “nfs_relative_file_path”

    Correct Command is:

    nutanix@cvm$ vdisk_manipulator –operation=”add_fingerprints” –nfs_container_name=”ctr_name” –nfs_relative_file_path=”vdisk_path”

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