Filesystems

This page serves to give some information on possible filesystems for Linux machines, in particular those that may be used for very large filesystems (many TB). The list is sorted by age!

XFS

• SGI's filesystem (1994) that was ported to Linux around 2001
• no 16 TB limitation; max size is 8 Eib (1 exbibyte = 2^60 bytes)
• no data compression and checksumming (data-integrity) features. It does have metadata checksums.

ZFS

• Sun's filesystem which is natively available on Solaris (since 2005)) and OpenSolaris (both of which are freely available)
• no 16 TB limitation; max size is 2^128 bytes
• (optional) transparent (gzip) compression (LZO compression available as patch)
• atomic updates - means that the on-disk state is consistent at all times, there's no need to perform a lengthy filesystem check after forced reboots/power failures
• background checksumming and self-healing for data integrity
• Built-in stripes (RAID-0), mirrors (RAID-1) and RAID-Z (it's like software RAID-5, but more efficient due to ZFS's copy-on-write transactional model)
• triple parity raid (raidz3) has been added to ZFS [1]
• there are ports of ZFS to FreeBSD and Mac OS X
• the source code license of ZFS is incompatible with the GPL of the Linux kernel, therefore only available as userland filesystem (ZFS-over-FUSE; see see http://www.wizy.org/wiki/ZFS_on_FUSE) on Linux
• installable ZFS/FUSE packages are available e.g. on latest Ubuntu und Fedora (see http://www.linux-magazine.com/w3/issue/103/ZFS.pdf)

Ext4

• fairly new in Linux kernel (stable since 2008); ext4 is based on ext3 (same developers)
• becoming the default of new versions of Linux distros (Fedora, Ubuntu, ...)
• no 16 TB limitation; max size is 1 EiB (1 exbibyte = 2^60 bytes)
• no compression and checksumming (data-integrity) features

btrfs

• latest addition to native Linux filesystems; considered stable since 2.6.31 kernel (2009; see http://www.h-online.com/open/Kernel-Log-2-6-31-Tracking--/features/113671)
• no 16 TB limitation; max size is 16 Eib (1 exbibyte = 2^60 bytes)
• (optional) transparent (zlib) compression
• checksumming for data integrity is implemented
• a review of btrfs from an ex-ZFS engineer: http://lwn.net/Articles/342892/
• you can upgrade an existing linux file system to btrfs without destroying the existing fs or duplicating the data: http://btrfs.wiki.kernel.org/index.php/Conversion_from_Ext3
• http://www.h-online.com/open/The-Btrfs-file-system--/features/113738