#Requires -Version 5.1
<#
    JbTecWiz Support Centre -- generated fix script

    Fault : iSCSI targets disconnect, or disks appear offline after a reboot
    Fix   : Give the storage a redundant path and the right network
    Source: https://jbtecwiz.com/support/srv-sto-iscsi

    Run as     : Elevated PowerShell
    Expect     : 90 minutes
    Risk       : high
    Reversible : yes

    WHEN THIS IS THE RIGHT FIX
    Sessions drop during use.

    HOW TO UNDO IT
    MPIO can be removed with Uninstall-WindowsFeature, though not while
    paths depend on it.

    This script walks the fix one step at a time and asks before each
    one. Steps with no command are things you do yourself -- it prints
    those and waits. Run with -DryRun to print without executing.

    --------------------------------------------------------------------
    NO WARRANTY - USE AT YOUR OWN RISK

    This script is provided by JbTecWiz as-is and with no warranty of any
    kind, express or implied. You run it entirely at your own risk.

    JbTecWiz accepts no liability for any loss or damage arising from its
    use, including but not limited to data loss, downtime, or configuration
    changes that turn out to be wrong for your system.

    You are responsible for reading this script before running it, for
    satisfying yourself that it suits the machine in front of you, and for
    having a working backup first. Some steps cannot be undone.
    --------------------------------------------------------------------
#>

[CmdletBinding()]
param(
    # Print every step and command without running anything.
    [switch]$DryRun,
    # Do not ask before each step. Read the script first if you use this.
    [switch]$Unattended
)

$ErrorActionPreference = 'Stop'
$script:Failed = 0

function Write-Rule { param([string]$Text)
    Write-Host ''
    Write-Host ('-' * 70) -ForegroundColor DarkGray
    if ($Text) { Write-Host $Text -ForegroundColor Cyan }
}

function Show-Prose { param([string]$Text, [string]$Colour = "Gray")
    if (-not $Text) { return }
    $words = $Text -split "\s+"; $line = "  "
    foreach ($w in $words) {
        if (($line.Length + $w.Length) -gt 74) { Write-Host $line -ForegroundColor $Colour; $line = "  " }
        $line += "$w "
    }
    if ($line.Trim()) { Write-Host $line -ForegroundColor $Colour }
}

function Invoke-Step {
    param(
        [int]$Number, [string]$Do, [string]$Why,
        [scriptblock]$Command, [switch]$Manual, [string]$Shell = "powershell"
    )
    Write-Rule "  Step $Number of 6"
    Show-Prose $Do "White"
    if ($Why) { Write-Host ""; Show-Prose $Why "DarkGray" }

    if ($Manual) {
        Write-Host ''
        Write-Host '  -> Do this yourself, then press Enter to carry on.' -ForegroundColor Yellow
        if (-not $Unattended -and -not $DryRun) { [void](Read-Host) }
        return
    }

    Write-Host ''
    foreach ($l in ($Command.ToString().Trim() -split "`n")) {
        Write-Host ("    " + $l.Trim()) -ForegroundColor Green
    }
    Write-Host ''

    if ($DryRun) { Write-Host "  (dry run -- not executed)" -ForegroundColor DarkGray; return }
    if (-not $Unattended) {
        $a = Read-Host "  Run this step? [Y]es / [S]kip / [Q]uit"
        if ($a -match "^[Qq]") { Write-Host "  Stopped at your request."; exit 0 }
        if ($a -match "^[Ss]") { Write-Host "  Skipped." -ForegroundColor DarkGray; return }
    }
    try { & $Command }
    catch {
        $script:Failed++
        Write-Host ("  Step $Number failed: " + $_.Exception.Message) -ForegroundColor Red
        Show-Prose "The rest of the fix may depend on this. Read the write-up before carrying on." "Red"
        if (-not $Unattended) {
            $c = Read-Host "  Carry on anyway? [y/N]"
            if ($c -notmatch "^[Yy]") { exit 1 }
        }
    }
}

Write-Rule
Write-Host '  iSCSI targets disconnect, or disks appear offline after a reboot' -ForegroundColor White
Write-Host '  Give the storage a redundant path and the right network' -ForegroundColor Cyan
Write-Host ''
Write-Host '  Risk: high   Reversible   90 minutes'
Write-Host ''
Show-Prose 'No warranty. Use at your own risk - JbTecWiz accepts no liability. Read it before you run it, and have a backup.' 'DarkYellow'
Write-Rule

if (-not $Unattended -and -not $DryRun) {
    $go = Read-Host '  Ready? [y/N]'
    if ($go -notmatch "^[Yy]") { Write-Host "  Nothing was changed."; exit 0 }
}

Invoke-Step -Number 1 -Do 'Read the events to see whether the target or the network went away.' -Command {
    Get-WinEvent -LogName System -MaxEvents 200 | Where-Object ProviderName -like '*iScsiPrt*' | Format-Table TimeCreated,Id,Message -Wrap
}

Invoke-Step -Number 2 -Do 'Check whether MPIO is installed and claiming the devices.' -Why 'Without MPIO, two paths to the same LUN present as two separate disks, and the operating system will happily corrupt the filesystem by writing through both. It is not an optional optimisation on a multi-path SAN.' -Command {
    Get-WindowsFeature Multipath-IO | Format-Table Name,InstallState
    Get-MPIOAvailableHW
    mpclaim -s -d
}

Invoke-Step -Number 3 -Do 'Install and configure MPIO for iSCSI.' -Command {
    Install-WindowsFeature Multipath-IO -Restart
    Enable-MSDSMAutomaticClaim -BusType iSCSI
    Set-MSDSMGlobalDefaultLoadBalancePolicy -Policy RR
}

Invoke-Step -Number 4 -Do 'Put storage traffic on dedicated adapters and a separate subnet or VLAN, with no default gateway on the storage interfaces.' -Command {
    Get-NetAdapter | Format-Table Name,InterfaceDescription,LinkSpeed,Status
    Get-NetIPConfiguration | Format-Table InterfaceAlias,IPv4Address,IPv4DefaultGateway
}

Invoke-Step -Number 5 -Do 'Turn off any power saving on the storage adapters, and disable flow control or enable it consistently at both ends -- a mismatch causes exactly this pattern of drop.' -Manual

Invoke-Step -Number 6 -Do 'Raise the disk timeout so a brief path failure does not fail the I/O.' -Command {
    Set-ItemProperty 'HKLM:\SYSTEM\CurrentControlSet\Services\Disk' -Name TimeOutValue -Value 60 -Type DWord
}

Write-Rule "  Confirm it worked"
Show-Prose 'Both paths are active, and pulling one cable does not interrupt I/O.' 'White'
Write-Host ''
if (-not $DryRun) {
    mpclaim -s -d 0
    Get-IscsiSession | Format-Table TargetNodeAddress,IsConnected,NumberOfConnections
}

Write-Rule
if ($script:Failed -gt 0) {
    Write-Host ("  Finished with " + $script:Failed + " failed step(s).") -ForegroundColor Yellow
    Show-Prose 'Read the full write-up at https://jbtecwiz.com/support/srv-sto-iscsi' 'Yellow'
} else {
    Write-Host '  Finished.' -ForegroundColor Green
}
Write-Host ''
Show-Prose 'To undo: MPIO can be removed with Uninstall-WindowsFeature, though not while paths depend on it.' 'DarkGray'
Write-Rule