General Discussion

Difference Between Linux OS And ISCSI Volume


A customer has 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 someone help explain the reason for this difference 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


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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