Tuesday, 13 February 2018

How Many Items does Read-NcDirectory Return?

I had an email conversation with a colleague regards something I had written. Specifically - http://www.cosonok.com/2015/07/search-ncfilesystemps1-cdot.html - which morphed a year-and-a-half later into the better - http://www.cosonok.com/2017/02/treesize-for-clustered-ontap-get.html. My colleague commented “you use the read-directory, but that doesn’t return all records (only first 2000 or so)” so I had to prove this was not the case.

In the following post - all using PowerShell and the Data ONTAP PowerShell Toolkit - I set up a test SVM, test volume, and create 100’000 files in my test volume, and then run Read-NcDirectory on that volume to see how many results come back.


PS> Import-Module DataONTAP
PS> Connect-NcController 10.9.3.10
PS> Get-NcVserver
PS> Get-NcAggr

PS> New-NcVserver -Name SVM_TEST -RootVolume ROOTVOL -RootVolumeAggregate data1 -RootVolumeSecurityStyle UNIX

PS> New-NcVol TEST_VOL data1 10g -JunctionPath /TEST_VOL -VserverContext SVM_TEST


The next bit will create the 100’000 files in the volume.


PS> For($i=1;$i -le 100000;$i++){Write-Host "$i " -NoNewLine; Write-NcFile "/vol/TEST_VOL/file$i" -Data "$i" -VserverContext SVM_TEST}


It will take some time to create 100’000 files (a couple of hours on my VSIM). You can check the filecount is increasing by running df -i on the Clustershell CLI.

And when that’s finished we see if Read-NcDirectory can return the 100’000+ records (Read-NcDirectory will take a while to process).


PS> $R = Read-NcDirectory -path /vol/TEST_VOL -VserverContext SVM_TEST
PS> $R.count
100003


And visual proof!

Image: Read-NcDirectory returning > 100’000 records - Picture 1

Image: Read-NcDirectory returning > 100’000 records - Picture 2: $R Output

I could keep running my test with ever larger file count and see if there is a limit, but for now we’ll leave it at “Read-NcDirectory definitely returns over 100’000 records, and I don’t know if there is a limit.”

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