Linux Conference
October 26- 28, 2011
Prague , Czech Republic
Linux Development Center
The Extended FAT file system
Differentiating with FAT32 file system
Keshava Munegowda , Venkatraman S
Texas Instruments (India) Pvt Ltd
Bangalore.
Dr. G T Raju
1
Professor and Head, Computer Science and Engineering Department,
R N S Institute of Technology, Bangalore, India.
ExFAT
Linux Development Center
Agenda
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FAT file system
Need for ExFAT file system
ExFAT file system organization
Boot Sector of FAT and ExFAT
Snapshot of Boot Sector of ExFAT
Directory Entries of FAT
Directory Entries of ExFAT
Clusters Heap
Up-Case Table
Snapshot of Root directory
Performance Benchmarking in Linux
Performance Benchmarking in Windows
References
ExFAT
Linux Development Center
FAT File system
BPB
FAT1
FAT2
Cluster 2
Cluster 3
Cluster 4
………….
………….
………….
Minimum 1
sector
BPB - BIOS Parameter Block
– BIOS : Basic Input-Output System
– Also Called as “Boot Sector” or “Volume Boot Record”
– Specifies
• Number of sectors in the storage partition/disk/device
• Number of FATs ( File Allocation Table)
• Sectors per cluster
FAT1 – File Allocation Table
Data
clusters
-
Linear linking (chain) of data clusters of the
file/directory
FILE.TXT
cluster3
cluster7
EOF
FAT2 – Backup of FAT1
Data clusters
-
Group of physical/logical sectors/blocks
- Contains directories or Files data
3
Clusters chain / Linked list of
clusters
ExFAT
Linux Development Center
Need For ExFAT file system
l
FAT File system limited to support only
32GB.
–
FAT does not support Higher size SDXC cards.
Security features
–
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NTFS
–
–
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Optional for Removable storage devices
4
Meta data overhead for file/directory
Write caching mechanism for performance
optimizations causes the data corruption in when
removable storage device is unplugged.
ExFAT
Linux Development Center
ExFAT file system Organization
BPB
FAT1
FAT2
Cluster 2
Cluster 3
Cluster 4
………….
………….
………….
2.
3.
24
Sectors
l
l
l
l
Exists only if
TexFAT file
system
Cluster heap
Up Case Table
1.
Volume label
Directory Entry
Allocation bit map
Directory Entry
Up case directory
entry
12 Sectors for Boot Area
Another 12 sectors for backup of
Boot Area
FAT2 exists if the TexFAT (
Transactional FAT is used)
First few Data clusters starting
from cluster 2 contains
–
–
Cluster allocation bit map table
Up case table
Cluster allocation Bit map
Directory Entry
Up-case Table Directory Entry
Volume label Directory Entry
l
Next Cluster Contains
–
Data clusters
–
5
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