Filesystems: Difference between revisions

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(New page: Actually, ZFS is available on Linux too as a user space filesystem, and Sun are considering a kernel port: http://www.wizy.org/wiki/ZFS_on_FUSE However, I'm inclined to wait for btrfs (bu...)
 
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Actually, ZFS is available on Linux too as a user space filesystem, and Sun are considering a kernel port:
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).
http://www.wizy.org/wiki/ZFS_on_FUSE


However, I'm inclined to wait for btrfs (butter-fs). Here's a review of btrfs from an ex-ZFS engineer:
== Ext3 ==
http://lwn.net/Articles/342892/
* fairly old, but well established and well behaved
* does not support more than 16GB
* does not support transparent compression
* does not support checksumming (a data-integrity feature)


Oracle are working on a new generation NFS replacement designed specifically to benefit from some of the btrfs features:
== Ext4 ==
http://oss.oracle.com/projects/crfs/
* fairly new in Linux kernel (since 2.6.27 or so)
* becoming the default of new Linux distros
* no 16 GB limitation
* no compression and checksumming (data-integrity) features


Here's an article one of the truely astonishing btrfs features: You can upgrade an existing linux file system to btrfs without destroying the existing fs or duplicating the data!
== XFS ==
http://btrfs.wiki.kernel.org/index.php/Conversion_from_Ext3 well, what are the alternatives?
* SGI's filesystem that was ported to Linux some years ago
* no 16 GB limitation
* no compression and checksumming (data-integrity) features


- ext3 does not support more than 16GB,
== ZFS ==
- ext4 does but is too young and lacks the features of zfs and btrfs
* Sun's filesystem which is natively available on Solaris and OpenSolaris (both of which are freely available)
- xfs also does but lacks the features of zfs and btrfs, and requires at least a good UPS. Bad XFS crashes are not unheard of.
* there are ports of ZFS to FreeBSD and Mac OSX
- don't know about jfs
* the source code license of ZFS is incompatible with the GPL of the Linux kernel; nevertheless Sun is considering a kernel port (see http://www.wizy.org/wiki/ZFS_on_FUSE) 
* available as userland filesystem (ZFS-over-FUSE) on Linux;  installable packages are available e.g. on latest Ubuntu und Fedora (see http://www.linux-magazine.com/w3/issue/103/ZFS.pdf)


All four do not support compression.
== btrfs ==
 
* latest addition to native Linux filesystems; stable version since 2.6.31 kernel (http://www.h-online.com/open/Kernel-Log-2-6-31-Tracking--/features/113671)
It should be clear that a 100 TB filesystem requires some kind of backup. And tape backup itself is tricky and costly to get right.
* 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
Currently, I would setup a Solaris fileserver with ZFS because ZFS is mature and the filesystem can be read by FreeBSD and Linux. A few months ago I tried an OpenSolaris installation CD and it worked like a charm.
* http://www.h-online.com/open/The-Btrfs-file-system--/features/113738
 
One possibility in Linux is ZFS over FUSE; this has a large number of advantages over other filesystems (except Btrfs) - see http://www.linux-magazine.com/w3/issue/103/ZFS.pdf . The article explains installation for Ubuntu. I must admit that I did not try it so far.
 
The alternative would be Btrfs, see http://www.h-online.com/open/The-Btrfs-file-system--/features/113738 . This is available for latest Fedora and Ubuntu, is part of the recently released 2.6.31 kernel (http://www.h-online.com/open/Kernel-Log-2-6-31-Tracking--/features/113671), and will therefore in the future be available in all distros.
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