UDF: A Multi Platform Filesystem
fleetingTable of Contents
- 1 How to have a file system in an external drive accessible from windows/mac/linux ? :
- 1.1 FAT32 :
- 1.2 NTFS :
- 1.3 UDF :
- 1.4 Comparison of udf, ntfs, ext :
- 1.4.1 Size limits :
- 1.4.2 Metadata :
- 1.4.3 Features :
- 1.4.4 Allocation and layout policies :
- 1.4.5 Supporting operating systems :
- 1.5 Conclusion :
- 1.6 Test mkudffs for real
- 2 Permalink
1 How to have a file system in an external drive accessible from windows/mac/linux ? :
1.1 FAT32 :
Accessible everywhere, but is limited to 4Go…
1.2 NTFS :
Good drivers on linux (NTFS-3G), but philosophically bad.
The specification has become open ?
1.3 UDF :
Should be the best option.
- https://en.wikipedia.org/wiki/Universal_Disk_Format “is an open vendor-neutral file system for computer data storage for a broad range of media”
- http://serverfault.com/questions/35243/what-is-the-partition-id-filesystem-type-for-udf
- http://superuser.com/questions/39942/using-udf-on-a-usb-flash-drive
- http://www.neowin.net/forum/topic/604926-format-usb-drive-to-udf-filesystem/
1.4 Comparison of udf, ntfs, ext :
https://en.wikipedia.org/wiki/Comparison_of_file_systems
1.4.1 Size limits :
| File system | Maximum filename length | Allowable characters in directory entries | Maximum pathname length | Maximum file size | Maximum volume size |
|---|---|---|---|---|---|
| ext4 | 255 bytes | Any byte except NUL and / | No limit defined | 16 TB | 1 EB |
| NTFS | 255 characters | Depends on namespace used | 32,767 UCS with each path component (directory or filename) up to 255 characters long | 16 EB | 16 EB |
| UDF | 255 bytes | Any Unicode except NUL | 1,023 bytes | 16 EB | 2 TB (hard disk), 8 TB (optical disc) |
1.4.2 Metadata :
| File system | Stores file owner | POSIX file permissions | Creation timestamps | Last access/ read timestamps | Last content modification timestamps | Disk copy created | Last metadata change timestamps | Last archive timestamps | Access control lists | Security/ MAC labels | Extended attributes/ Alternate data streams/ forks | Checksum/ ECC | Max Timestamp Granularity |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| ext4 | Yes | Yes | Yes | Yes | Yes | Unknown | Yes | No | Yes | Yes | Yes | Yes | 1 nanosecond |
| NTFS | Yes | Yes | Yes | Yes | Yes | No | Yes | No | Yes | Yes | Yes | No | 100 nanoseconds |
| UDF | Yes | Yes | Yes | Yes | Unknown | Unknown | Yes | Yes | Yes | No | Yes | No | Unknown |
1.4.3 Features :
| File system | Hard links | Symbolic links | Block journaling | Metadata-only journaling | Case-sensitive | Case-preserving | File Change Log | Snapshot | XIP | Encryption | COW | integrated LVM | Data deduplication | Volumes are resizeable |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| ext4 | Yes | Yes | Yes | Yes | Yes | Yes | No | No | Yes | Yes | No | No | No | Online |
| NTFS | Yes | Yes | No | Yes | Yes | Yes | Yes | Partial | Yes | Yes | Partial | Unknown | No | Online |
| UDF | Yes | Yes | Yes | Yes | Yes | Yes | No | No | Yes | No | No | No | No | Unknown |
1.4.4 Allocation and layout policies :
| File system | Block suballocation | Variable file block size | Extents | Allocate-on-flush | Sparse files | Transparent compression |
|---|---|---|---|---|---|---|
| ext4 | No | No | Yes | Yes | Yes | No |
| NTFS | Partial | No | Yes | No | Yes | Partial |
| UDF | No | No | Yes | Depends | No | No |
1.4.5 Supporting operating systems :
| File system | DOS | Windows 9x | Windows NT | Linux | Mac OS | Mac OS X | FreeBSD | BeOS | Solaris | AIX | z/OS | OS/2 | Windows CE | Windows Mobile | VxWorks | HP-UX |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| ext4 | No | No | with Ext2Fsd (partial, extents limited) or Ext2Read (read-only, also on LVM2) | Yes since kernel 2.6.28 | No | with fuse-ext2 (partial) and ExtFS (full read/write) | No | Unknown | Unknown | Unknown | Unknown | Unknown | No | Unknown | Unknown | Unknown |
| NTFS | with third-party driver | with third-party driver | Yes | Yes Kernel 2.2 or newer, or with NTFS-3G or ntfsprogs | No | with NTFS-3G | with NTFS-3G | with NTFS-3G | with NTFS-3G on Opensolaris | Unknown | Unknown | Partial read-only third-party driver | with 3rd-party driver | No | Unknown | Unknown |
| UDF | Unknown | Partial read-only support of UDF 1.02 since Win98 and WinME | Yes | Yes | Yes since Mac OS 9 | Yes | Yes | Unknown | Yes | Unknown | Unknown | Unknown | Yes | Unknown | Unknown | Unknown |
1.5 Conclusion :
UDF is THE true universal file system. The drawback on using UDF is that is possesses less features that others. But the essentials are there. It also suffers from bad OS implementations that will consider a UDF filesystem as being a read only CD-Rom.
1.6 Test mkudffs for real
http://superuser.com/questions/39942/using-udf-on-a-usb-flash-drive#answer-48040
Zeroing the disk to avoid any confusion later.
dd if=/dev/zero of=/dev/sdx bs=512
Creating the new filesytem.
mkudffs --media-type=hd --blocksize=512 /dev/sdx
It worked perfectly on a 1Go micro sd card.