The df_netapp and df_netapp32 checks tried to determine 64 bit counters by checking
the existance of the oid .22.214.171.124.4.1.7126.96.36.199.1.29.1 (df64TotalKBytes).
Depending on the 64 Bit counter a df_netapp check is created, otherwise df_netapp32 is used.
Unfortunately not all netapp interfaces start at .1, so some netapp devices where wrongly
inventorized as df_netapp32 checks.
Those checks reported negative volume sizes whenever the 32 bit counter overflowed.
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