Assistance with Log Analytics Disk Query

Hairy_Zeus

Maybe this?

Perf
//| where Computer !startswith "A" //or Computer startswith "J" //testing
| where TimeGenerated > startofday(ago(1d))
| where CounterName in ( "% Free Space" , "% Used Space", "Free Megabytes")
| where InstanceName !contains 'Harddisk' and InstanceName != '_Total'
| summarize PctFree=avgif(CounterValue, CounterName == "% Free Space" ), 
            Linux  =avgif(CounterValue, CounterName == "% Used Space"), 
            MbFree =avgif(CounterValue, CounterName == "Free Megabytes"),
            arg_max(TimeGenerated, Computer) by Computer, InstanceName 
| extend PctFree = iif(isnan(PctFree),Linux,PctFree)
| project-away Linux, Computer1
| project TotalSizeGB=round(MbFree*100/PctFree/1024,0), 
            round(PctFree,2),
            round(MbFree,2), 
            Computer, 
            InstanceName
| summarize FreePCT=avg(PctFree) by Computer,
            InstanceName,
            TotalSizeGB,
            FreeGB = round(MbFree / 1024,2)
| sort by Computer asc, InstanceName asc
| project Computer, InstanceName, TotalSizeGB, FreeGB,  GBinUse = TotalSizeGB - FreeGB, FreePCT