Disparity between Linux system and iSCSI volume

GTHOMAS13 — Wed, 04 Jun 2025 12:29:53 GMT

We have observed a large disparity between the reported usage of a number of ISCSI volumes when querying from the NetApp in comparison to when querying from the OS.
In all cases, the NetApp is showing greater usage than the OS. I have included examples of this are below.
Please, can you explain the reason for this disparity and perhaps more crucially what happens when the server tries to write past the point of space availability as reported by the NetApp.

NetApp Output

iscsi_volume_data1

filer::> volume show iscsi_volume_data1
Vserver Volume Aggregate State Type Size Available Used%
--------- ------------ ------------ ---------- ---- ---------- ---------- -----
vserver iscsi_volume_data1 aggr1 online RW 200GB 42.14GB 78%

LUN config:

Name Size Avail Used%

data1 200GB 5.66GB 97.17%

Linux Output

Volume Size Used Avail Used% Mounted on

iscsi_volume_data1 197G 70G 117G 38% /data1

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Disparity between Linux system and iSCSI volume