Fedora 16 To Use "Btrfs" Filesystem By Default

as someone with a btrfs partition containing a handful of broken inodes (according to btrfsck), I'd say wait. btrfsck takes ages during each boot AND cannot fix problems. I'll switch back to ext4 when I find the time (and a plug compatible for my external drive.)

>this also means Fedora doesn't use LVM by default anymore

Uh, that's pretty big. How will I resize partitions on the fly?

Good point. The flipside of that is that such a distro is less suitable for production servers.

That said, a savvy sysadmin would be picky about the filesystem to use in production anyway and could easily use a non-default filesystem.

It's a tradeoff. On the other hand, you can more easily implement backup systems that copy directory trees, using hardlinks for files that haven't changed. For example.

I don't know the details of how specific filesystems are implemented, but it seems that if it's reasonable to achieve the locality you want, then it can be done for the first name a file has. Subsequent names wouldn't have good locality, but second and third links to a file are much less common. If you want other links to the file to have good locality, then simply make a copy, doubling your space requirements.

Hard links are useful, and you don't necessarily need to sacrifice locality in the common case, and in the uncommon case you can still choose between good locality, or good use of space and the sometimes useful semantics of two names by which to read or write a file.

The value of locality in this context assumes you use many of the files in the same directory at the same time, or enumerate a lot of directories and read the files. Your home directory has different access patterns than /lib or /bin.

That'd only really be true if a significant portion files were hardlinked. My root filesystem (Debian GNU/Linux testing) has 393,410 files, of which 825 have more than one link. My /home has 0 out of 156,273 files hardlinked.

Having 0.2% (or less) of files hardlinked shouldn't prevent storing files in the same directory near each other.

I agree that the change will cause a lot of pain, however early adopters tend to have a high tolerance for pain. If you don't want to deal with the pain or are running a server (your EC2 mention sounds like a server), you probably want to avoid cutting edge distros like Fedora.

Hey, I'd really appreciate it if you could send a report of your experiences to linux-ext4@vger.kernel.org. This is the first I've heard of issues with ext4 with EBS, and I'd love to know more. (Also, please mention the kernel version you are using; one possibility is that EC2 kernels tend to lag upstream kernels, and ext4 has had a lot of bug fixes since a RHEL or SLES kernel of 2.6.32/2.6.34 --- upstream is at 2.6.39, and we're about to release version 3.0. :-)

This is not a filesystem's job.