The way I would do it is to create millions of small files on the share (the number you'd need to create to generate alerts will depend on the size of the share). Here is a PowerShell command that will do that, you would just replace the large number with whatever suits your situation (the example will generate 100,000 files).
1..100000 | %{ ($_ * (Get-Random -Max ([int]::maxvalue))) > "\\path\to\share\file$_.txt"}