July 24, 2013

Tip 55: My Disk is a Cluster ****

My disk is a cluster size, of 4Kb. This is the default cluster size of an NTFS volume up to 16TB (http://support.microsoft.com/kb/140365). But is this the best size to use?

There are many performance whitepapers that recommend that other cluster sizes should be used for best performance of the disk subsystem. For instance here is a best practice for SQL Server; http://msdn.microsoft.com/en-us/library/dd758814(v=SQL.100).aspx. Other products may have different recommendations.

So how can you find the current disk cluster size?



A built in tool since Windows XP/2003. Can be used to view many file system settings. The cool thing about this tool is that it can be used on a Clustered Shared Volume to view the disk cluster size or on a regularly mounted drive with a drive letter.



Fsutil.exe fsinfo ntfsinfo c:clusterstoragevolume1

NTFS Volume Serial Number :       0x965c513b5c511779

NTFS Version   :                  3.1

LFS Version    :                  2.0

Number Sectors :                  0x000000000dbfe7ff

Total Clusters :                  0x00000000001b7fcf

Free Clusters  :                  0x00000000001b7847

Total Reserved :                  0x0000000000002004

Bytes Per Sector  :               512

Bytes Per Physical Sector :       512

Bytes Per Cluster :               65536

Bytes Per FileRecord Segment    : 1024

Clusters Per FileRecord Segment : 0

Mft Valid Data Length :           0x0000000000010000

Mft Start Lcn  :                  0x000000000000c000

Mft2 Start Lcn :                  0x0000000000000001

Mft Zone Start :                  0x000000000000c000

Mft Zone End   :                  0x000000000000cca0

Resource Manager Identifier :     ACDA0BE7-F86C-11E2-9402-002522F4122F



A Sysinternals tool. Can be used to view disk information when mounted to a drive letter.



Ntfsinfo.exe c:


NTFS Information Dump V1.01

Copyright (C) 1997 Mark Russinovich



Volume Size


Volume size            : 121601 MB

Total sectors          : 249040895

Total clusters         : 31130111

Free clusters          : 2949108

Free space             : 11519 MB (9% of drive)

Allocation Size


Bytes per sector       : 512

Bytes per cluster      : 4096

Bytes per MFT record   : 1024

Clusters per MFT record: 0

MFT Information


MFT size               : 404 MB (0% of drive)

MFT start cluster      : 786432

MFT zone clusters      : 3789728 – 3840928

MFT zone size          : 200 MB (0% of drive)

MFT mirror start       : 2

Meta-Data files




A built in tool. Can check disks for errors and fix errors. If you specify just a scan without fixing the summary will show the partition cluster size.



Chkdsk c:


The type of the file system is NTFS.

Volume label is OSDisk.

WARNING!  F parameter not specified.

Running CHKDSK in read-only mode.


CHKDSK is verifying files (stage 1 of 3)…

  414464 file records processed.

File verification completed.

  10980 large file records processed.

  0 bad file records processed.


CHKDSK is verifying indexes (stage 2 of 3)…

  529830 index entries processed.

Index verification completed.

  0 unindexed files scanned.

  0 unindexed files recovered.


CHKDSK is verifying security descriptors (stage 3 of 3)…

Security descriptor verification completed.

  57684 data files processed.

CHKDSK is verifying Usn Journal…

  34399264 USN bytes processed.

Usn Journal verification completed.


Windows has scanned the file system and found no problems.

No further action is required.

 124520447 KB total disk space.

 112460852 KB in 315323 files.

    188804 KB in 57685 indexes.

         0 KB in bad sectors.

    590355 KB in use by the system.

     65536 KB occupied by the log file.

  11280436 KB available on disk.

      4096 bytes in each allocation unit.

  31130111 total allocation units on disk.

   2820109 allocation units available on disk.



Windows Performance Toolkit

Part of the Windows 8 ADK or Windows 7 SDK. Can list partition cluster size on partitions mounted with a drive letter.



Run WPRUI.EXE after installing the WPT. Select the Disk I/O Activity scenario, although any scenario will work. Click start, you only have to run the capture for a few seconds, then click Save to save the trace. Remember to click Cancel to fully stop the WPRUI trace, then exit WPRUI.


After trace is taken Run WPA.EXE from the WPT, open the trace that was previously saved and select Menu->Trace->System Configuration->Storage and multiply the Sector/Cluster and the Bytes/Sector to get the partition cluster size.



There you go, many ways to confirm your partition cluster size after you have formatted your drive. Any other ways not mentioned, please let me know of any other cool tools.


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