How to Implement Multi-Server NTFS Access to iSCSI SAN Without Data Corruption


9 views

When multiple Windows servers simultaneously mount the same iSCSI target with NTFS formatting, you're essentially creating a distributed write scenario without proper locking mechanisms. This violates NTFS's fundamental design as a single-system filesystem, leading to:

  • Metadata corruption from competing writes
  • File system structure damage
  • Potential complete volume corruption

Since Microsoft Cluster Server isn't an option, consider these approaches:

Option 1: SMB Shares with DFS Namespace

Create a highly available SMB share using Windows Server's built-in capabilities:

# PowerShell to create DFS namespace
Import-Module DFSR
New-DfsnRoot -Path "\\Domain\SANShare" -TargetPath "\\Server1\SANShare" -Type DomainV2
Add-DfsnRootTarget -Path "\\Domain\SANShare" -TargetPath "\\Server2\SANShare"

Option 2: Storage Replica with Staggered Mounts

Implement asynchronous replication between servers with manual failover procedures:

# On primary server:
Enable-NetFirewallRule -DisplayName "Storage Replica*"
New-SRPartnership -SourceComputerName SRV1 -SourceRGName RG01 -SourceVolume D: -SourceLogVolume L: -DestinationComputerName SRV2 -DestinationRGName RG02 -DestinationVolume D: -DestinationLogVolume L: -LogSizeInBytes 2GB

For more enterprise-grade solutions:

MetaSan Implementation

MetaSan creates a distributed lock manager across Windows servers. Sample registry tweaks after installation:

Windows Registry Editor Version 5.00

[HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\MetaSan\Parameters]
"MaxLocks"=dword:00002710
"HeartbeatInterval"=dword:0000000a

StarWind Virtual SAN

Creates a clustered storage pool with automatic failover:

PS C:\> Add-ClusterDisk -InputObject (Get-Disk -Number 3)
PS C:\> Enable-ClusterStorageSpacesDirect

When implementing any shared storage solution:

  • Benchmark with CrystalDiskMark before deployment
  • Monitor with PerfMon counters for "Avg. Disk Queue Length"
  • Consider adding SSD caching if using spinning disks

Always maintain:

  1. Regular VSS snapshots of the iSCSI volume
  2. Scheduled chkdsk runs during maintenance windows
  3. Documented recovery procedures for when (not if) corruption occurs

When working with Windows Server 2008 and iSCSI SAN storage, the fundamental limitation is that NTFS isn't designed for concurrent write access from multiple machines. The scenario you're describing - multiple servers needing access to the same SAN volume - creates potential for catastrophic data corruption if not handled properly.

// THIS WILL CAUSE CORRUPTION:
Server1 → Mount iSCSI LUN (NTFS formatted)
Server2 → Mount same iSCSI LUN (NTFS formatted)
// Both servers now have direct NTFS write access simultaneously

While Microsoft Cluster Service (MSCS) solves this through coordinated access, you've rightly identified the constraints:

  • Budget limitations for Windows Enterprise licensing
  • Organizational policies preventing cluster implementations
  • Complexity overhead for simpler use cases

Here are viable approaches with sample implementation details:

1. SAN-Level File System (Like MetaSAN)

MetaSAN and similar solutions create a clustered filesystem layer:

// Conceptual architecture:
SAN LUN → MetaSAN Clustered FS → NTFS volumes for each server
// Servers see their own NTFS volume while sharing the same physical storage

2. Distributed File System Replication (DFSR)

Configure one server as primary with others syncing via DFS:

# PowerShell DFSR setup example:
New-DfsReplicationGroup -GroupName "SAN_Data" 
Add-DfsrMember -GroupName "SAN_Data" -ComputerName Server1,Server2,Server3
Set-DfsrMembership -GroupName "SAN_Data" -ContentPath "D:\SharedData"

3. SMB 3.0 Scale-Out File Server

If you can upgrade to Server 2012 or later:

# Create scale-out file share
New-SmbShare -Name ClusterShare -Path "D:\Data" -ContinuouslyAvailable $true
# All servers connect via SMB instead of direct iSCSI
net use Z: \\FileServer\ClusterShare

When evaluating these options, consider:

  • IOPS requirements: Some solutions add latency
  • Failover needs: How quickly must another server take over?
  • Locking behavior: Application compatibility with file locks

Here's a sample workflow for MetaSAN implementation:

1. Install MetaSAN client on all servers
2. On SAN:
   metasancfg --create-volume SharedVol --size 1TB
   metasancfg --export-volume SharedVol --to Server1,Server2
3. On each server:
   mount -t ntfs /dev/msan/SharedVol /mnt/shared
   chmod 777 /mnt/shared

Critical metrics to watch in any shared storage solution:

# Windows perfmon counters to monitor:
LogicalDisk(*)\Avg. Disk sec/Read
LogicalDisk(*)\Avg. Disk sec/Write
Network Interface(*)\Bytes Total/sec