I wrote about btrfs 8 years ago.
Since then, it has made its way into several small to mid-end storage solutions (more NAS inclined solutions) including Rockstor, Synology, Terramaster, and Asustor. In the Linux world, SUSE® Linux Enterprise Server and OpenSUSE® use btrfs as the default OS file system. I have decided to revisit btrfs filesystem to give some thoughts about its future.
Have you looked under the hood?
The sad part is not many people look under the hood anymore, especially for the market the btrfs storage vendors are targeting. The small medium businesses just want a storage which is cheap. But cheap comes at a risk where the storage reliability and data integrity are often overlooked.
The technical conversation is secondary and thus the lack of queries for strong enterprise features may be leading btrfs to be complacent in its development.
Creepy feelings of Raid 5/6 write hole
Perhaps the most glaring “hole” (pun intended) is this RAID 5/6 write hole issue posted btrfs wiki page. In the header, it states
Although an RFC patch was posted in August 2017 to fix this, there wasn’t any news if this issue was fixed. Even it was fixed, there aren’t any statements from the community or any responsible organization which has inspired confidence of btrfs production use in the industry.
Here is another statement stating the RAID 5/6 issue, this time from Rockstor.
I also found another unsavoury statement, this time coming from folks working on Clear Linux*, an up-and-coming Linux distribution from Intel. The paragraph below came from this article.
Thus, some vendors using btrfs have shunned this issue. Synology® advertises that their SHR (Synology® Hybrid RAID), which is based on Linux software MD/RAID. QNAP®, Synology’s competitor, took to issue of Synology’s btrfs implementation and ran a FUD page on btrfs. QNAP® itself runs ext4 file system but some of its newer systems are switching over to ZFS file system.
Not nearly almost production ready
There are certainly data integrity and reliability issues if and when certain conditions appear in the storage file system, and this a big no-no. Any enterprise and any storage file system with integrity issue is certainly not equipped to serve data to applications.
Whilst btrfs remains on the radar of a few Linux distributions like Ubuntu and Oracle Linux, RedHat® has deprecated btrfs in version 7.4 2 years ago and dropping it completed by omitted the btrfs driver in recently released version 8.0. Even Ubuntu is taking a liking to ZFS now.
The “experimental mode” of btrfs seems to be there like forever, and vendors are “getting the drift”. ZFS on Linux is gaining ground even though there are looming issues about the GPL vs CDDL licensing, which got Linus Torvalds all riled up. Still btrfs does not seem to have stepped up to be a mainstream enterprise file system, and this is disappointing.
View of its future
Given this less glossy out look, I do not see btrfs gaining any more ground to move up the ladder. Currently the list of production users is not impressive. Here are the companies listed:
Without a strong enterprise backing exception is Facebook) and with its present inefficiencies, I see a bleak future for this once promising file system.
