Veeam ReFS Repository on iSCSI Targets

Troubleshooting Repository Deadlocks

With Resilient Filesystem (ReFS) integration into Veeam Availability Suite 9.5 a whole bunch of features was integrated. One of the biggest advantages is ‘Fast Cloning Technology’ which enables synthetic full backups by merely creating pointers to already existing datablocks on the repository.

In a small scale environment I had a hardware repository server (Win 2016) with an iSCSI Volume as repository (ReFS, 64k) as primary backup target. This constellation worked like a Swiss watch. Daily backups ran for months without any trouble. Fast cloning technology enabled weekly synthetic full backups with minimal consumption of extra space.

Recently I’ve added another iSCSI Volume (ReFS, 64k) to be used as repository for backup copies. That’s when the fun began… Continue reading “Veeam ReFS Repository on iSCSI Targets”

Query NTFS Blocksize

Using 64k blocksize for better performance

Partitions with Veeam-Backups, SQL-Database files or SQL-Logs should be formatted with a 64k blocksize for better performance. You can check blocksizes with a simple command.

Open a CMD Shell with Administrator rights.

fsutil fsinfo ntfsinfo <Drive>

Example for the system partition.

fsutil fsinfo ntfsinfo C:
NTFS-Volumeseriennummer : 0xa892e42c92e400a4
Version : 3.1
Anzahl der Sektoren : 0x000000001dc807ff
Gesamtzahl Cluster : 0x0000000003b900ff
Freie Cluster : 0x0000000000b42c71
Insgesamt reserviert : 0x0000000000000ff0
Bytes pro Sektor : 512
Bytes pro physischen Sektor : 512
Bytes pro Cluster : 4096
Bytes pro Dateidatensatzsegment : 1024
Cluster pro Dateidatensatzsegment : 0
MFT-gültige Datenlänge : 0x0000000017180000
MFT-Start-LCN : 0x00000000000c0000
MFT2-Start-LCN : 0x0000000000000002
MFT-Zonenstart : 0x0000000000eb7240
MFT-Zonenende : 0x0000000000eb9340
RM-Bezeichner: FFFF0956-A102-11E7-87BD-005056C00008

You can see Bytes per Cluster: 4096 which equals 4KB.


To check all local partitions for the corresponding blocksize you can use a PS script, which was originally posted by Stuart Moore.

$wql = "SELECT Label, Blocksize, Name FROM Win32_Volume WHERE FileSystem='NTFS'"
Get-WmiObject -Query $wql -ComputerName '.' | Select-Object Label, Blocksize, Name


Stuart Moore – Get Cluster size for all disks and volumes on a Windows machine using powershell and wmi

Veeam Backup & Replication Best Practices