However, when you format the partition manually, you can specify cluster size 512 bytes, 1 KB, 2 KB, 4 KB, 8 KB, 16 KB, 32 KB, 64 KB in the format dialog box or as a parameter to the command line FORMAT utility.
#DISK FORMATTING WHY ARE CLUSTER SIZES IMPORTANT WINDOWS#
The following table shows the default values that Windows NT/2000/XP uses for NTFS formatting: Drive size (logical volume) Cluster size Sectorsĥ13 MB - 1,024 MB (1 GB) 1,024 bytes (1 KB) 2ġ,025 MB - 2,048 MB (2 GB) 2,048 bytes (2 KB) 4 It means that the bigger the cluster size, the more disk space is wasted, however, the performance is better. When file grows beyond the cluster boundary, another cluster is allocated. On NTFS if file is small enough, it can be stored in MFT record itself without using additional clusters. If you create file lets say 1 byte in size, at least one cluster should be allocated on FAT file system. NTFS Volume Source (created or converted from existing FAT volume).Ĭluster is an allocation unit.location and fragmentation of Master File Table (MFT) and paging file,.There are several factors (we do not mention here drive type, rpm. Other techniques like disk defragmentation could help you either. Windows 2000 cannot defrag a partition if the cluster size is larger than 4 KByte.If you investigate your storage needs, you can tune some of global NTFS parameters to achieve significant increase of disk performance.A large cluster size (16-32 KByte) is good when the partition will contain large files (Fileserver, video-editing, etc.),Īs it will lower the possibility of file fragmentation, and also makes the File Table (Maps files to what clusters they uses) smaller.A small cluster size (4 KByte) is good when the partition will contain lots of small files,.Repeat until optimal cluster-size is found.Ĭonsiderations about choosing cluster-size:.Benchmark the partition using the disk critical application.Format the partition with the new cluster-size.It depends on the HDD, Controller (If RAID also the selected Stripe-Size), Filesystem (FAT,NTFS, etc.)Īnd the application itself. Memory, but there is no standard optimal cluster-size which can be applied for every disk criticalĪpplication in every environment. Usually an cluster-size of 4 KByte seems to be a good choice as it matches the page size used in In WinNT the /FS parameter specifies filesystem (NTFS/FAT16/FAT32) and /A specifies cluster size (aka Allocation-unit):.With the parameter /Z one can specify a multiplier of sector size (Standard 512 bytes), so if using 8, then one will get a cluster size of 4096 bytes: In Win95 OSR2 and beyond it is possible to specify the cluster-size when formatting (Before the choice was made for you).To format a partition with specific cluster size: To check the cluster size of an already formatted partition (Where X is the partition letter): Important if having many files/directories with long filenames in the root like on a floppy disk. Note the VFAT (Virtual-FAT) is an extension of the FAT16 to support long filenames,īut it can halve the amount of max files/directories because it uses an extra entryįor storage of each long filename (If the filename is beyond the 8.3 mask). There is also a limit in Win2k/XP not to create and format FAT32 partitions beyond 32 GByte to encourage usage of NTFS. Which cannot allocate enough memory to handle a file allocation table (FAT) larger than 16 MByte. Note the 16 Bit limit in FAT32 is only important if planning to use 16 bit disk tools such as DOS scandisk, When a basic disk is converted to a dynamic disk, then any volumes that existed on the basic disk will still only be able to extend into unformatted areas next to them using diskpart. Note the abilities of the NTFS volumes are dependent on whether they are placed on basic or dynamic disks. Note the different filesystems(FAT, FAT32, NTFS, etc.) can impose a Max Cluster Count and Max Cluster Size. There is the following relation between Cluster Count, Cluster Size and Partition Size:Ĭluster Count * Cluster Size = Partition Size This would create a so called "slack" of 2 KByte. So if having a 10 KByte file and a 4 KByte cluster-size, the file would occupy 3 clustersĪnd 12 KByte space. When formatting a HDD-partition it is divided into clusters with a certain cluster-size.Ī cluster is a group of sectors and can can only be occupied by one file, The sector-size is defined during the low-level format performed by the HDD-manufacture (Standard 512 Bytes). The physical HDD is divided into sectors, which is the smallest unit of storage possible.