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authorPatrick Spek <p.spek@tyil.nl>2022-03-05 16:48:20 +0100
committerPatrick Spek <p.spek@tyil.nl>2022-03-05 16:48:20 +0100
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Add new blogpost on replacing reiserfs
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+---
+date: 2022-03-05
+title: Deprecating ReiserFS
+tags:
+- BTRFS
+- Filesystems
+- GNU+Linux
+- ReiserFS
+- ZFS
+- bcachefs
+---
+
+[ReiserFS is getting deprecated from Linux](https://lkml.org/lkml/2022/2/20/89),
+mostly due to it not being ready for the year 2038. This is a little sad, as I
+still use it on some systems for storing the Gentoo Portage tree, and the Linux
+kernel sources. It works well for this because it supports
+[tail packing](https://en.wikipedia.org/wiki/Block_suballocation#Tail_packing),
+a form of block suballocation, which can save disk space.
+
+So, what alternatives are there for ReiserFS? After asking around and reading
+some comments around the Internet, I've narrowed it down to 3 potential
+candidates, bcachefs, btrfs, and zfs. Each comes with their own pros and cons,
+as things tend to do.
+
+## bcachefs
+
+There are several downsides for bcachefs for me. The first one I found was that
+the documentation on their main site seems a bit lacking, followed shortly by
+finding that there are no ebuilds for it in Gentoo.
+
+Since it was suggested several times on comments on a certain orange site, I
+asked around if it at least supported block suballocation, which is the main
+reason I would want to use it anyway. The answer came back as a "no", so I could
+safely ignore it for the rest of the journey.
+
+## BTRFS
+
+BTRFS seems like a more serious contender. It supports block suballocation, and
+has good enough documentation. As an additional benefit, it is supported in the
+mainline Linux kernel, making it easy to use on any modern setup. There are a
+few issues, such as having to rebalance in certain situations, and this
+rebalancing can itself cause issues. The files I'm storing are relatively easily
+recreated with a single git clone, or downloading a tarball and unpacking that,
+so that doesn't have to be problematic to me.
+
+## ZFS
+
+The final contestant, ZFS, supports block suballocation and has great
+documentation. It is not part of the mainline Linux kernel, however, so this may
+make things more complex on some systems. I run ZFS already on a few machines,
+but not all, so where it is not used already, it is a drawback.
+
+Since my main concern is storing many small files, I created a few logical
+volumes (and 1 ZFS subvol) and cloned the main reason for wanting a filesystem
+with block suballocation, the [Gentoo Portage
+tree](https://github.com/gentoo/portage). The cloning itself was done with
+`--depth=1`.For reference, I also created an ext4 volume.
+
+```
+/dev/mapper/edephas0-test.btrfs 5.0G 559M 3.8G 13% /tmp/test/btrfs
+/dev/mapper/edephas0-test.ext4 4.9G 756M 3.9G 17% /tmp/test/ext4
+/dev/mapper/edephas0-test.reiserfs 5.0G 365M 4.7G 8% /tmp/test/reiserfs
+tyilstore0/test 5.0G 1.1G 4.0G 21% /tmp/test/zfs
+```
+
+Looking at the output from `df -h`, ReiserFS seem to still be a clear winner
+when it comes to storing many small files. Nothing is even close. What does
+surprise me, however, is that ZFS is actually resulting in the largest space
+requirement. I'm not sure why this is, as it should support block suballocation
+just fine according to [the filesystem comparison chart on
+Wikipedia](https://en.wikipedia.org/wiki/Comparison_of_file_systems#Allocation_and_layout_policies).
+
+BTRFS comes out as the next best option, after ReiserFS, so that'll be what I am
+going to use on my systems for storing large trees of small files.