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Monitoring with PowerShell: Monitoring disk speed

Sometimes we get complaints from clients reporting “my machine is slow” and not really get any leads to work with. The client just experiences slowness. In most cases this is due to disk speeds – the client bought some cheap computer with a 5400RPM spinner in it and is expecting it to perform just as good as any machine we supplied with an SSD.

To prevent this we could look at things such as the disk queue explained in an earlier blog here. But the problem with this type of monitoring is that its quite intermittent; You often only find the issue after a user has already complained. Because of this I’ve created a monitoring set that runs once or twice a (work) day in our RMM system. This script simply does a quick test on how fast it can actually create and read files and is used for reporting on it.

The script

So the script uses Diskspd.exe by Microsoft. You can download diskspd.exe here. You have to download the file and host it somewhere yourself. The script then downloads diskspd.exe from this location and executes two commands; a read of a 50mb file for 30 seconds, and writing a 50mb file for 30 seconds, totaling to 1 minute of performance testing.

$DownloadURL = "https://example.com/diskspd.exe"
Invoke-WebRequest -Uri $DownloadURL -OutFile "C:\Windows\Temp\diskspd.exe"
$ReadTest =  & "C:\Windows\Temp\diskspd.exe" -b128K -d30 -o32 -t1 -W0 -S -w0 -c50M test.dat
$Writetest = & "C:\Windows\Temp\diskspd.exe" -b128K -d30 -o32 -t1 -W0 -S -w100 -Z128K -c50M test.dat
$ReadResults = $readtest[-8] | convertfrom-csv -Delimiter "|" -Header Bytes,IO,Mib,IOPS,File | Select-Object IO,MIB,IOPs
$writeResults = $writetest[-1] | convertfrom-csv -Delimiter "|" -Header Bytes,IO,Mib,IOPS,File | Select-Object IO,MIB,IOPS

$ReadResults and $WriteResults will contain the IO, Mib/ps and IOPS. You can alert on each of these values. My personal preference is alering on them when the Mib/ps drops below 500mbps, because then you can be fairly sure its either a spinning disk, performance issue, or ancient SSD that needs to be replaced.

And that’s all for today! as always, happy PowerShelling.

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