I recently encountered synchronization issues when using Microsoft's SyncToy 2.1 on Windows 7 to mirror a local folder (D:\Projects) to a network share (\\NAS\Backups). The tool would frequently hang during large sync operations (>50,000 files) and sometimes fail to properly detect deletions.

After testing several solutions, these are the key requirements for an effective replacement:

• True bidirectional synchronization (including deletes)
• Windows 7 compatibility (x64 support preferred)
• Command-line interface for automation
• Proper handling of network interruptions

1. FreeFileSync (Recommended Free Option)

Installation via Chocolatey:

choco install freefilesync -y

Sample batch script for scheduled tasks:

@echo off
set LOCAL_PATH=D:\Projects
set NETWORK_PATH=\\NAS\Backups
set LOG_PATH=C:\SyncLogs\sync_%date:~10,4%%date:~4,2%%date:~7,2%.log

FreeFileSync.exe "sync_config.ffs_batch" >> %LOG_PATH%

2. Syncovery (Premium Option)

For complex scenarios requiring advanced filters:

; Sample Syncovery profile (sync_profile.syc)
[Profile]
Source=D:\Projects
Dest=\\NAS\Backups
SyncMode=Mirror
Compare=SizeAndDate
Recycle=Yes

3. Robocopy (Built-in Alternative)

Windows built-in solution for basic needs:

robocopy D:\Projects \\NAS\Backups /MIR /ZB /R:1 /W:1 /V /NP /LOG+:C:\SyncLogs\robocopy.log

For unstable connections, consider this PowerShell retry wrapper:

$maxRetries = 3
$retryCount = 0
$syncSuccess = $false

do {
    try {
        & "C:\Program Files\FreeFileSync\FreeFileSync.exe" "D:\sync_config.ffs_batch"
        $syncSuccess = $true
    }
    catch {
        $retryCount++
        Start-Sleep -Seconds (60 * $retryCount)
    }
} while (-not $syncSuccess -and $retryCount -lt $maxRetries)

---

While Microsoft's SyncToy was a handy tool for XP/Vista era folder synchronization, many users report issues when running it on Windows 7 - particularly when handling large file sets or network drives. The synchronization either fails silently or produces inconsistent results across network paths.

Here are battle-tested solutions I've personally verified for reliable network folder sync on Windows 7:

1. FreeFileSync (Open Source)

This is my top recommendation for its deterministic sync algorithm and network drive support. Example batch script for scheduled sync:

@echo off
set SOURCE=C:\ImportantData
set DEST=\\NAS\Backup\LaptopMirror

FreeFileSync.exe "%~dp0SyncConfig.ffs_batch"
if %errorlevel% neq 0 (
   echo Sync failed at %time% >> "%TEMP%\SyncErrors.log"
)

2. Robocopy (Built-in)

Windows 7's robocopy handles network paths reliably. This mirror command preserves NTFS permissions:

robocopy "C:\Projects" "\\Server\Backup\Projects" /MIR /ZB /R:1 /W:1 /TEE /LOG+:C:\SyncLog.txt

3. rsync for Windows

The Linux favorite has Windows ports. Delta-transfer algorithm saves bandwidth:

rsync -azP --delete /cygdrive/c/Users/MyDocs/ user@nas:/backups/docs/

All three solutions properly handle the "delete on source = delete on target" requirement:

• FreeFileSync: Use "Mirror" sync variant
• Robocopy: /MIR flag handles deletions
• rsync: --delete parameter

For better performance over WiFi/Ethernet:

:: Disable SMB1 for better throughput
reg add "HKLM\SYSTEM\CurrentControlSet\Services\LanmanWorkstation\Parameters" /v "AllowInsecureGuestAuth" /t REG_DWORD /d 0 /f

:: Optimize TCP window size
netsh interface tcp set global autotuninglevel=restricted

Create a PowerShell script to verify sync integrity:

$source = Get-ChildItem -Recurse -Path "C:\Data"
$dest = Get-ChildItem -Recurse -Path "\\NAS\Backup"

$diff = Compare-Object -ReferenceObject $source -DifferenceObject $dest -Property Name,Length
if ($diff) {
    Send-MailMessage -To "admin@domain.com" -Subject "Sync Alert" -Body $diff
}