FSx ONTAP LUNs assigned to windows instances. How to see actual free space in OS

Hello,

Thank you for writing to us.

I believe you have created an iSCSI LUN [1] of 16TB from an ONTAP Filesystem of 16TB storage capacity.

Upon mounting this LUN to windows OS, it will be presented to the initiator as a Disk with some overhead to the disk configuration, then filesystem headers once it is initialized and further the partition headers once volume is created. Then you would be writing data to the volume. iSCSI Client or initiator could only have view & control up to this level, and not the savings at volume or aggregate level from where LUN was created.

For iSCSI server side usage and available space iSCSI Target or ONTAP file system need to be referred. For the usage and free space at AWS FSx Ontap file system level we have cloudwatch metrics [2] [3]. Also you may use Ontap CLI for space utilization [4].

Hence it is not possible for the Client side OS to view the free space at SSD File System or LUN back end level.

[1] https://docs.aws.amazon.com/fsx/latest/ONTAPGuide/create-iscsi-lun.html [2] https://docs.aws.amazon.com/fsx/latest/ONTAPGuide/file-system-metrics.html [3] https://docs.aws.amazon.com/fsx/latest/ONTAPGuide/monitor-fs-storage.html [4] https://docs.netapp.com/us-en/ontap/volumes/commands-display-space-usage-reference.html