iSCSI Best Practices for Windows Server and FlashArray

Registry Keys

Subkey: HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\Tcpip\Parameters\Interfaces\<Interface GUID>
Entry: TcpAckFrequency
Value Type: REG_DWORD
Valid Range: 0-255
Default: 2
New Setting: 1

Subkey: HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\Tcpip\Parameters\Interfaces\<Interface GUID>
Entry: TcpNoDelay
Value Type: REG_DWORD
Valid Range: 0-1
Default: 0
New Setting: 1

​This image illustrates the new settings.

The machine should be rebooted after making any of these registry changes.

PowerShell to Add or Change Registry Keys

This is a snippet of a example script that will enumerate all of the network adapters on a system and require the user to enter the adapter name(s) they wish to apply the settings to. This script is not all-inclusive to every environment and should be tested thoroughly before running in production.
The individual script is available in the Pure PowerShell Example Scripts repository. The Pure Storage PowerShell Toolkit also contains a cmdlet to perform this configuration. The machine should be rebooted after making any of these registry changes.

<# Script to disable Nagle (TcpNoDelay) and TcpAckFrequency on a per adapter basis.#>
        $AdapterNames = @()
        Write-Host "All available adapters: "
        Write-Host " "
        $adapters = Get-NetAdapter | Sort-Object Name | Format-Table -Property "Name", "InterfaceDescription", "MacAddress", "Status"
        $adapters
        Write-Host " "
        $AdapterNames = Read-Host "Please enter all iSCSI adapter names to be tested. Use a comma to seperate the names - ie. NIC1,NIC2,NIC3"
        $AdapterNames = $AdapterNames.Split(',')
        Write-Host " "
        Write-Host "Adapter names being configured: "
        $AdapterNames
        Write-Host "==============================="
        foreach ($adapter in $AdapterNames) {
            $adapterGuid = (Get-NetAdapterAdvancedProperty -Name $adapter -RegistryKeyword "NetCfgInstanceId" -AllProperties).RegistryValue
            $RegKeyPath = "HKLM:\system\currentcontrolset\services\tcpip\parameters\interfaces\$adapterGuid\"
            $TAFRegKey = "TcpAckFrequency"
            $TNDRegKey = "TcpNoDelay"
            ## TcpAckFrequency
            if ((Get-ItemProperty $RegkeyPath).$TAFRegKey -eq "1") {
                Write-Host ": TcpAckFrequency is set to disabled (1). No action required."
            }
            if (-not (Get-ItemProperty $RegkeyPath $TAFRegKey -ErrorAction SilentlyContinue)) {
                Write-Host ": TcpAckFrequency key does not exist."
                Write-Host "REQUIRED ACTION: Set the TcpAckFrequency registry value to 1 for $adapter ?" -NoNewline
                $resp = Read-Host -Prompt "Y/N?"
                if ($resp.ToUpper() -eq 'Y') {
                    Write-Host "Creating Registry key and setting to disabled..."
                    New-ItemProperty -Path $RegKeyPath -Name 'TcpAckFrequency' -Value '1' -PropertyType DWORD -Force -ErrorAction SilentlyContinue
                }
                else {
                    Write-Host "WARNING" -ForegroundColor Yellow -NoNewline
                    Write-Host ": TcpAckFrequency registry key exists but is enabled. Changing to disabled."
                    Set-ItemProperty -Path $RegKeyPath -Name 'TcpAckFrequency' -Value '1' -Type DWORD -Force -ErrorAction SilentlyContinue
                }
            }
            if ($resp.ToUpper() -eq 'N') {
                Write-Host "ABORTED" -ForegroundColor Yellow -NoNewline
                Write-Host ": Registry key not created or altered by request of user."

            }
            ## TcpNoDelay
            if ((Get-ItemProperty $RegkeyPath).$TNDRegKey -eq "1") {
                Write-Host ": TcpNoDelay (Nagle) is set to disabled (1). No action required."
            }
            if (-not (Get-ItemProperty $RegkeyPath $TNDRegKey -ErrorAction SilentlyContinue)) {
                Write-Host "REQUIRED ACTION: Set the TcpNodelay (Nagle) registry value to 1 for $adapter ?" -NoNewline
                $resp = Read-Host -Prompt "Y/N?"
                if ($resp.ToUpper() -eq 'Y') {
                    Write-Host "TcpNoDelay registry key does not exist. Creating..."
                    New-ItemProperty -Path $RegKeyPath -Name 'TcpNoDelay' -Value '1' -PropertyType DWORD -Force -ErrorAction SilentlyContinue
                }
                else {
                    Write-Host "WARNING" -ForegroundColor Yellow -NoNewline
                    Write-Host ": TcpNoDelay registry key exists. Setting value to 1."
                    Set-ItemProperty -Path $RegKeyPath -Name 'TcpNoDelay' -Value '1' -Type DWORD -Force -ErrorAction SilentlyContinue
                }
            }
            if ($resp.ToUpper() -eq 'N') {
                Write-Host "ABORTED" -ForegroundColor Yellow -NoNewline
                Write-Host ": TcpNoDelay registry key not created or altered by request of user."
            }
        }