Backup all user and system databases except for TEMPDB. Compress all SQL backups to local disk using 7zip. Copy backups to multiple locations based on configurations. Get MD5 hash for multiple locations and roll back the copy if the hashes don't match.

SimplePowershellBackupSystem.ps1

Import-Module -Name SqlServer 

# CONFIGURATIONS:

$locationA = "C:\temp\share1"
$locationB = "C:\temp\\share2"
$local = "C:\temp"
$SqlServerLocation = "SQLSERVER:\SQL\localhost\DEFAULT\Databases"
$retries = 5

Set-Location $SqlServerLocation

# backup all user and system databases except for TEMPDB

foreach ($database in (Get-ChildItem -force) | Where { $_.Name -ne 'tempdb'} ) 
{
    $dbName = $database.Name

    Backup-SqlDatabase -Database $dbName -BackupFile "$local\$dbName.bak"

}

# Compress all SQL backups to local disk using 7zip

dir "$local\*.bak" | ForEach-Object { & "7z.exe" a $_.BaseName $_.Name }

# copy backups to multiple locations based on configurations
# get MD5 hash for multiple locations and roll back the copy if the hashes don't match

$count=0
do{
Get-ChildItem "$local" -Filter *.7z | Foreach-Object {
    start-transaction
    copy-item $_.FullName -Destination $locationA
    copy-item $_.FullName -Destination $locationB
    Get-FileHash $locationA\$_ -Algorithm MD5 | select -ExpandProperty Hash > $locationA\$_.hash
    Get-FileHash $locationB\$_ -Algorithm MD5 | select -ExpandProperty Hash > $locationB\$_.hash
    $hashLocationA = Get-FileHash $locationA\$_ -Algorithm "MD5"
    $hashLocationB = Get-FileHash $locationB\$_ -Algorithm "MD5"
    If ($hashLocationA.HashString -ne $hashLocationB.HashString){
        undo-transaction
                                                        }
    else {
        remove-item $_.FullName
        complete-transaction
        $success = $true
    }
    
            
$count++

                                                    }
}until($count -eq $retries -or $success)
if(-not($success)){exit}