I created a 100GB CIFS volume with the space guarantee set to none, snapshot reserve 10% on a netapp SIM ONTAP 9.2. There are no snapshots yet. I copied a 10GB file to this share and checked the space usage:
cluster1::> df -h /vol/accounting/ Filesystem total used avail capacity Mounted on Vserver /vol/accounting/ 90GB 10GB 79GB 11% /accounting cifs_svm /vol/accounting/.snapshot 10GB 0B 10GB 0% /accounting/.snap shot cifs_svm
Then I deleted the file and got the following result of the df command:
cluster1::> df -h /vol/accounting/ Filesystem total used avail capacity Mounted on Vserver /vol/accounting/ 90GB 592MB 89GB 1% /accounting cifs_svm /vol/accounting/.snapshot 10GB 0B 10GB 0% /accounting/.snapshot cifs_svm
It seems that these 592MB are used by Performance Metadata.
Vserver : cifs_svm Volume : accounting
Feature Used Used% -------------------------------- ---------- ------ User Data 24KB 0% Filesystem Metadata 6.56MB 0% Inodes 32KB 0% Snapshot Reserve 10GB 10% Performance Metadata 586.5MB 1%
Total Used 10.58GB 11%
Total Physical Used 593.2MB 1%
NetApp docs say that this is the amount of space used by performance optimization activities and there is no direct method to control it, so there is really not much to do about that? Will it increase significantly in the future?
A newly-created FlexVol volume with a space guarantee of none or file uses free space equal to 0.005 × its nominal size.
Your case: 100GB x 0.005 = 0.5GB x 1024 = 512MB, this is an approximate space I believe that will by taken away as 'metadata' purpose.
As I interpret, the keyword here is 'newly-created flexcol' so it should be one time deduction. You can try to verify it by increasing size to 150GB or whatever, sorry I don't have access to my NetApp lab at the moment.