Btrfs is a copy-on-write CoW filesystem for Linux aimed at implementing advanced features while focusing on fault tolerance, repair, and easy administration. Ext4 is safe and stable and can handle large filesystems with extents, but why switch? While it is true that Btrfs is still considered experimental and is growing in stability, the time when Btrfs will become the default filesystem for Linux systems is getting closer.
Some Linux distributions have already begun to switch to it with their current releases. Down the road, new clustered filesystems will readily take advantage of Btrfs with its copy on write and other advanced features for their object stores.
Ceph is one example of a clustered filesystem that looks very promising, and can take advantage of Btrfs. Typing long Btrfs commands can quickly become a hassle. Each command besides the initial btrfs command can be reduced to a very short set of instructions. This method is helpful when working from the command line to reduce the amount of characters typed.
Shorten each of the longer commands after the btrfs command by reducing them to their unique, shortest prefix. In this context, unique means that no other btrfs commands will match the command at the command's shortest length. The shortened version of the above command is:. No other btrfs commands start with fi ; filesystem is the only one.
The same goes for the de sub-command under the filesystem command. In the example above, replace N with the partition number and X with the disk letter that is to be formatted. For example, to format the third partition of the first drive in the system with Btrfs, run:. It is possible to convert ext2, ext3, and ext4 filesystems to Btrfs using the btrfs-convert utility. The following instructions only supports the conversion of filesystems that are unmounted. To convert the root partition, boot to a system rescue disk SystemRescueCD works nicely and run on the conversion commands on the root partition.
Check the integrity of the filesystem using the appropriate fsck tool. In the next example, the filesystem is ext Btrfs supports transparent compression using the zlib, lzo, and zstd  compression algorithms.
The compress mount option sets the default behavior to compress all the newly created files. To re-compress the whole filesystem, run the following command:. Depending on the CPU and disk performance, using lzo compression could improve the overall throughput.
It is possible to use the zlib compression algorithm instead of lzo. Zlib is slower but has a higher compression ratio:.A file system is a logical collection of files on a partition or disk, And partition is a container for information and can span an entire hard drive if desired. All files and directories are created and managed under this root directory.
Since root directory stands on the top of file system, it has no parent directory. Besides root directory, every directory has a parent directory.File Systems as Fast As Possible
Linux allows us to create as many files and directories as we want. We can create files under the existing directories or may create new directories. Now you have a good idea about what the Linux file system is. Ext4 is the default file system on most Linux distributions for a reason. The reason that Ext4 is often recommended is that it is the most used and trusted filesystem out there on Linux today. It is used in massive data centers and in production, on all types of hard drives, including solid-state drives.
Not having journaling allows it to save on write space which is limited on SSDs. Also, it has a more modern architecture, which makes it quite fast when accessing data. In addition, BtrFS also has a robust snapshot feature, which allows users to create and roll-back changes to the system instantly. By far, XFS can handle large data better than any other file system on this list and do it reliably too. However, many Linux users shy away from it as not every Linux distribution supports it in their installation tool.
We have our own trusted good old filesytem, that has maybe limits in features and performance, but has never let us down. New filesystems are available, and they promise wonderful things. Yes, BTRFS was really unstable at the beginning, but if you read about huge data corruption problems in a blog post or topics like that, and that post was written inwell maybe things have changed since then.
The most important part of a file system is its on-disk format, that is the format used to store data onto the underlying media. There are few reasons: first, as I said, people are scared of change when it comes to filesystems. Why changing from a trusted and known one, to something new? Second reason, probably, the fast development cycles. While the on-disk format is finalized, the code base is still under heavy development to always improve performance and introduce new features.
And the examples he brings are the best proof about BTRFS: they are using the filesystem at Facebook, where they store production data. Well, because it has some great features! That number means 16 EiB of maximum file size and file system, and yes the E means Exabyte. This is possible thanks to the way it consumes space: other file systems use disks in a continguous manner, layering their structure in a single space from the beginning to the end of the disk.
Each disk, regardless its size, is divided into pieces the chunks that are either 1 GiB in size for data or MiB for metadata. Chunks are then grouped in block groupseach stored on a different device.
The number of chunks used in a block group will depend on its RAID level. Data protection and striping is done directly by the filesystem, so you can have different volumes that have inner redundancy:. So, a chunk is consumed on disk1, and its mirror is stored in another device, Disk 2 in the picture. In this way, if we lose Disk1, another copy of the block is still available on Disk2, and another copy can be immediately recreated for exaple on Disk3 using the free chunk. XFS takes seconds to complete the operations and it was performance bound by its log system; EXT4 took seconds to complete the test, and its limit comes from the fixed inode locations.
Both limits are the results of their design, and overcoming of those limits was one of the original goal of BTRFS. Did they succeed? Other features are worth a mention: — Writable and read-only snapshots — Checksums on data and metadata crc32c : this is great in my view, as every stored block is checked, so it can immediately identify and correct any data corruption — Compression zlib and LZO — SSD Flash storage awareness: another sign of a modern filesystem.
This results in larger write operations and faster write throughput.
Is anybody using btrfs without issues?
But as always, you have to decide if the features available in a given technology are worth the migration to it, and if the few limits are going to affect you. We stress-tested it on a secondary backup server that is running Ubuntu File system operations slow to an abysmal crawl.
The worst part is filesystem maintenance. This was running on a generously provisioned host, so I was able to keep upping the guest RAM until we could complete the operation — with a mere GiB of RAM required and just over 5. Granted this is not a normal use case, but compared to other filesystems it was a complete choke. Btrfs is not properly stable even now in but if you base your views on an operating system with a kernel from about you are not really fair to btrfs.
It went from two hours per backup down to 3 minutes on average. Only been running for a week, but speed has been great. I chose to wipe my previous backups before starting, moving one backup into an hourly.I'm putting together a file server and planned on using an ext4 formatted SSD as the boot disk and a spare 2. From what I've read, data corruption tends to occur while editing large files like a virtual disk for a VM due to how copy-on-write is implemented and btrfs is, in theory, well suited to my application.
At the same time, a quick search of the forum results in lots of threads about btrfs pools and RAID arrays breaking, so I was hoping to get a better idea of how it's working for people using it. My btrfs setup worked awesome for well over a year until I screwed it up through lack of knowledge.
Btrfs at Facebook
And even then, I didn't lose any data or have to go to my backups. I found it very stable and easy to use. The big trick really is to understand the btrfs raid levels because btrfs-raid1! Avoid heavy usage databases, VM images, etc if you're going to use it.
Stick to light no more than a few users NAS-style file storing usage. Do not go any longer between backups than you are categorically willing to lose data. If you're good with all that, then btrfs might work well for you. You're still going to be more likely to have filesystem issues than you would with other filesystems, though, even after all that.
So I suppose the question really becomes, what do you actually want from btrfs? Jim is wise. It scares me. Thanks for the feedback. The features I want are storage pooling and checksumming. Either ZFS or btrfs would be suitable but I figured that since my demands were pretty low, ZFS and the resource requirement would be overkill. Exordium01 wrote: Either ZFS or btrfs would be suitable but I figured that since my demands were pretty low, ZFS and the resource requirement would be overkill.
ZFS doesn't really have a large resource requirement. You won't get anywhere near the benefit from the ARC you normally would, and I'd strongly advise you not to load it up with hundreds of snapshots at a time, but aside from that you're good to go.
Aside from "testing btrfs", I really can't think of a use-case that calls for btrfs more than it calls for ZFS. Oh, and because btrfs is in the kernel. I've been running btrfs on a couple of machines at home for about a year or so now. I've not had so much as a sniff of a problem. I'm so so sorry. Every day I get home I pray that I will have suffered extensive data corruption - but no - it just seems to work. Yeah, I used it and, indeed, still use it for ages, and it just worked.
Until I hit ENOSPC, or one day the filesystem wouldn't mount, and the kernel that fixed that did mount the filesystem but deleted all the data. There are lots of people using btrfs without issues! I'm probably going to go with ZFS Ubuntu based on this thread, but btrfs does have some neat features, like the ability to reshape pools without reformatting, that would be convenient to have.
But ultimately the fact that it all performs unpredictably and frequently awfully AND is an easy order of magnitude, if not more, likely to eat your data makes it all moot. Unless you're the kinda person who'd date a serial killer, if they were cute.Facebook is growing rapidly, and like all cloud computing services faces resource utilization challenges.
This page describes some of the solutions Btrfs is providing in production now in Facebook's data centers. Tupperware is Facebook's containerization solution. Tupperware previously set up a container filesystem from scratch every time it started a task, which was expensive in terms of IO and CPU.
Using Btrfs' snapshot featuresTupperware can now snapshot a preexisting Btrfs image. Lack of true process isolation: The creation of a container filesystem from scratch gives each task a separate view of the filesystem, but this view is not truly isolated from other tasks running on the machine. One task can easily affect the root filesystem of another task on the machine, without the user explicitly configuring the tasks to share pieces of the filesystem.
Even worse, a task can overwrite data stored in packages used by other tasks. High IO expense for administrative tasks: A large number of IO operations were required to restart, move, or update Tupperware.
This IO was necessary even if all the data needed by the task was already on the destination machine. These IOs were happening during task starts, which makes matters worse as the task is down while we perform these operations.
There were also a number of expensive checks that Tupperware did just to ensure that other tasks didn't break anything on the machine, due to the poor isolation. Determinism: In the existing setup Tupperware does lots of IO operations to prepare the task to run.
Each of these operations can fail in many different ways. In addition, the configuration for these operations is not fully contained in the task specification, but also comes from outside configuration programs. This creates a situation where lots of variables have to align in just the right way for the setup to work. The image-based setup truly isolates tasks.
One task cannot accidentally change the filesystem of another task on the host. In addition, a setup like this opens the door to true multi-tenancy, where different tasks run on the same server.
Only a small number of IO operations are needed in the image-based setup if all data needed to start the task is already on the host. Moreover, it's possible to effectively share the common pieces of the root filesystem between the tasks while having full isolation.
Since task isolation is also now possible, checks that were needed only because of poor isolation are no longer needed, eliminating that IO overhead. The image-based approach allows the encapsulation of all filesystem configuration of the task in the task spec itself. No matter where or when the task starts the same operations are performed. An additional benefit is greater configurability left in the hands of the task owner.
The new setup is also designed around very few atomic operations: they either fully work and always produce the same result or fail completely.Before you start reading: if concepts like partitions, logical volumes or file system are not clear in your mind, I highly suggest you to read this article.
BTRFS aims to implement advanced featuresfault tolerance and ease administration. Another filesystem of this kind is ZFS. In the end a subvolume is shown by the operating system as a directory. Although many fixes were merged in Linux 4.
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BTRFS: what is it and why is it great? Image courtesy of Martin Abegglen. The following two tabs change content below. Bio Latest Posts. The IT guy with a slight look of boredom in his eyes. Current interests: Kubernetes, Tensorflow, shiny new things. Latest posts by mark see all. How to install NextCloud 17 on Ubuntu Leave a Reply Cancel reply.I wrote before in a blog entry about btrfs stability.
That was almost exactly seven years ago. The issue I had back then about a hard link limit of hard links in the same directory was fixed a long time ago. Since then btrfs has come a long way.
The most significant development was that SUSE started using btrfs as root file system and put several developers to work on finding and fixing bugs. Simultaneously only few new features were added. This significantly improved stability at least for the root file system use case. As just hinted, the main problem is that each developer just looks after their set of use cases.
So, developers from Facebook mainly look at their use case of using btrfs on their HDFS storage nodes. They have redundancy etc.
SuSE, as said, uses it as root file system system fileswhere there are single disks or, at most, mirrored disks. This, combined, was guaranteed to cause problems when seriously using btrfs as UrBackup storage. The most persistent issue was premature ENOSPC, where btrfs has an error saying it is out of space, remounting the file system read-only, even though there is still a lot of free space both for data and metadata available on the disk s.
The problem seems to be solved on the systems I observe with Linux 5. When using UrBackup seriously large number of clients with many simultaneous backups e. For example, writeback throttling was significantly improved a few years ago. This example improves the memory management, making Linux more able to handle the mixed database and archival workload mentioned above. Not to say that all errors are fixed.
For example, I recently learned that a call to synchronize the file system to make sure that data is actually written to disk does not return errors on Linux. Another important consideration is performance. One thing w. So, you can ask btrfs to list all files having data at e. Managing the backref metadata comes with the cost of having more metadata in general, though. Operations such as writing new data to files, deleting files, deleting snapshots, etc.
Btrfs goes to great lengths making this fast, though delayed backrefs etc. There is a number of unique features of btrfs which could be implemented because of the presence of back-references:. The performance problem with backrefs is that if a file has a lot of reflinks or snapshots, it may have a lot of backrefs. Running one of the operations above then involves a lot of iteration through all backrefs, making this operation unusably slow. UrBackup naturally creates a lot of snapshots and may reflink certain files many times.