Hi,
I hope someone might be able to help here. I am having trouble with net-snmp
reporting wrong size information for large file systems i.e. around 24TB but I
think this problem applies to anything larger that 2 or 4TB.
I am getting the same results upon net-snmp 5.7.2.1 (pre-compiled by Michael
Perz and available uponhttp://www.perzl.org ) and for release 5.7.3 which I
compiled upon the AIX platform (release obtained from official website yesterday
18/12/2017). Both installations are upon AIX 7.1.3 64 bit O/S.
The df -k of the large file system gives
Filesystem 1024-blocks Free %Used Iused %Iused Mounted on
/dev/datalv 25765609472 23711578832 8% 5 1% /data
and the snmpwalk output relevant to the /data file systems is below
UCD-SNMP-MIB::dskPath.7 = STRING: /data
UCD-SNMP-MIB::dskDevice.7 = STRING: /dev/datalv
UCD-SNMP-MIB::dskTotal.7 = INTEGER: 2147483647
UCD-SNMP-MIB::dskAvail.7 = INTEGER: 2147483647
UCD-SNMP-MIB::dskUsed.7 = INTEGER: 2054030640
UCD-SNMP-MIB::dskPercent.7 = INTEGER: 24
UCD-SNMP-MIB::dskPercentNode.7 = INTEGER: 0
UCD-SNMP-MIB::dskTotalLow.7 = Gauge32: 4290772992
UCD-SNMP-MIB::dskTotalHigh.7 = Gauge32: 1
UCD-SNMP-MIB::dskAvailLow.7 = Gauge32: 2236742352
UCD-SNMP-MIB::dskAvailHigh.7 = Gauge32: 1
UCD-SNMP-MIB::dskUsedLow.7 = Gauge32: 2054030640
UCD-SNMP-MIB::dskUsedHigh.7 = Gauge32: 0
As the size of the file system requires 64bits to be stored then obviously the
dskTotal and dskAvail are going to be wrong as they are 32bit registers. My
understanding is that in the case of large file systems, use is then made of the
Low and High registers of the same name. On the Internet I saw that these
registers were to be placed next to each other to form a 64 bit number.
i.e. dskTotalLow = 4290772992 = 0xFFC00000
dskTotalHigh = 1 = 0x1
Total = 0x1FFC00000 = 8585740288k
so Total is around 8TB and not the 24TB displayed in the df -k statement.
Have I got the logic wrong here or is this some bug on AIX? I have seen from
other explanations that this is working upon Linux systems so I suspect, if not
my mistake, then AIX system calls are tripping up the code by working slightly
differently.
I hope someone might be able to help.
Regards
Patrick------------------------------------------------------------------------------
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