Exchange 2013 Mailbox Server – NTFS allocation unit size

When we allocate LUN for Exchange 2013 Mailbox Server it is always best practise to put the disk in GPT mode with 64K NTFS allocation unit size on simple volume. In higher end Exchange Infrastucture we normally move to create mount point for LUN instead of all assign drive letter for each LUN. The above things are mostly known things.

If there is question to find out NTFS allocation unit size of the existing infrastructure then we will be unable to find them over GUI. Thought to share the easy steps on how to move forward.

1. List out the mount point in your Exchange Mailbox Server –

Go to Command Prompt type MountVol


Possible values for VolumeName along with current mount points are:






2. Use the fsutil to find the NTFS allocation unit size

C:\Users\exadmin>fsutil fsinfo ntfsinfo E:\Ex-DatabaseVolume01\
NTFS Volume Serial Number :       0x34c23257c2321e14
Version :                         3.1
Number Sectors :                  0x000000007ffbefff
Total Clusters :                  0x0000000000fff7df
Free Clusters  :                  0x0000000000faadd7
Total Reserved :                  0x0000000000000000
Bytes Per Sector  :               512
Bytes Per Physical Sector :       <Not Supported>
Bytes Per Cluster :               65536
Bytes Per FileRecord Segment    : 1024
Clusters Per FileRecord Segment : 0
Mft Valid Data Length :           0x0000000001180000
Mft Start Lcn  :                  0x000000000000c000
Mft2 Start Lcn :                  0x0000000000000001
Mft Zone Start :                  0x000000000000c040
Mft Zone End   :                  0x000000000000cca0
RM Identifier:        92E4AAAA-4645-11E3-AC43-0050569424DA

3. Divide the Bytes Per Cluster by Bytes Per FileRecord Segment (65536/1024 = 64 KB). It is acceptable to go 64KB size for Database File since the edb files are larger. The reason to have the same for log files is they are 1024KB (1MB) in size so 16 blocks would be needed for each one.



About Raji Subramanian

Nothing great to say about me...Just want to share my knowledge for others that will be useful at any moment of time when they stuck in critical issue....
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