Frequently asked questions…

btrfs

What is btrfs?

It’s a ‘next generation’ filesystem.

Another filesystem, don’t we have enough of those already?

Well, it offers a lot more than more traditional filesystems that’s why it’s considered next generation.

If it stores files, what more do I want from it?

Well, it supports copy-on-write and snapshots to help keep your data safe. These mean that when you write a new version of a file, the old one is unchanged, the new one is written separately, so if the power goes down, your data is still there. Snapshots allow you to roll back to previous versions of files, without using up the amount of disk space and time that backups require. So I don’t need to back up? Of course you do, what happens if you get a hardware failure? But btrfs does help there too as every file is checksummed so any corruption is detected. If you’re using a RAID system, btrfs even knows which of the copies is bad and replaces it with the good one.

RAID? That’s another hassle to set up—adding extra disk then sorting out all the partitions.

Btrfs does more than store files, it also handles RAID internally, you just tell it which disks you want it to use. It also deals with its own volume management.

What? Like LVM?

Similar. You set up a single btrfs volume, which can be a single disk or spanning extra disks in a RAID, then you create subvolumes, which are analogous to LVM logical volumes. Volumes can be added and removed at will, as can disks in the RAID. It means everything is done together, instead of separate layers at each stage.

What about encryption?

Ah, no btrfs doesn’t do that yet, but you can put a btrfs filesystem on encrypted devices.

It’s new, so is it safe?

It’s now considered stable – although the RAID 5/6 implementation isn’t yet – and suitable for most use, although using it with a recent kernel is advised. SUSE has been championing the use of btrfs for several years.

It sounds a bit like ZFS— why not just use that?

Many of the concepts are similar, but ZFS is proprietary. Oracle released the source code to an older version, but that means it will never get the features of later versions. There are also licensing concerns, which is why ZFS isn’t in the Linux kernel, while btrfs is. Interesting, where can I find more information. The btrfs wiki at http://btrfs.wiki.

kernel.org has plenty of information on btrfs—except how to pronounce btrfs!