Btrfs Is Getting There, But Not Quite Ready For Production 268
An anonymous reader writes "Btrfs is the next-gen filesystem for Linux, likely to replace ext3 and ext4 in coming years. Btrfs offers many compelling new features and development proceeds apace, but many users still aren't sure whether it's 'ready enough' to entrust their data to. Anchor, a webhosting company, reports on trying it out, with mixed feelings. Their opinion: worth a look-in for most systems, but too risky for frontline production servers. The writeup includes a few nasty caveats that will bite you on serious deployments."
Read their website (Score:5, Informative)
It says "experimental." They appreciate you helping them test their file system out. I appreciate it too, so please do. But remember that you are testing an experimental filesystem. When it eats your data, make sure you report it and have backups.
Happy with XFS (Score:3, Informative)
I've been happily using the XFS file system since the early-to-mid-2000s and have never had a problem. It is rock solid and much faster than ext3/ext4 in my experience, tested a lot longer than Btrfs, and handles the millions and millions of small files on redditmirror.cc very effectively.
Re:replace ext3 and ext4? really? (Score:4, Informative)
Lots of production servers user Ext filesystems. If btrfs is all it should be it will certainly replace these file systems one day soon as the safe choice.
Sure people use other filesystems on production Linux servers, but those are not the norm. The safe "Enterprise" (Not necessarily a good thing) choice is still Ext based filesystems.
ZFS (Score:5, Informative)
Meanwhile ZFS announced that it was ready for production [theregister.co.uk] last month.
http://zfsonlinux.org/ [zfsonlinux.org]
Re:Happy with XFS (Score:4, Informative)
Your happy with XFS because your machine has never lost power or crashed. If either of those things happened with the older versions of XFS it was nearly a 100% guarantee you would lose data. Now i'm told its more reliable.
So, if you told me you have been running it for the last year and it was reliable I would have given you more credit than claiming you have been running it for a decade and its been reliable. Because, its had some pretty serious issues that if you didn't hit them means your not a good test case.
I'm still skeptical, because AKAIK, XFS still doesn't have an order data mode.
Re:Happy with XFS (Score:5, Informative)
Your happy with XFS because your machine has never lost power or crashed. If either of those things happened with the older versions of XFS it was nearly a 100% guarantee you would lose data. Now i'm told its more reliable.
I don't know about being more reliable. I use XFS on my RAID array (mdadm) at home. I'm running the latest version of Linux Mint (Nadia), and if I ever lose poser and don't unmount that file system cleanly it looses all recent changes to the drive (and "recent" sometimes stretches to hours ago). The drive mounts fine and nothing appears corrupted (so I guess its not completely data loss), but any files changes (edits, additions, or deletions) to the file system are simply gone.
Its gotten to the point where if I've just put a lot of stuff on the drive I unmount it and then remount it just to make sure everything gets flushed to disk. If I ever get a chance to rebuild that array it most certainly will be using something different.
Re:Happy with XFS (Score:5, Informative)
No, that's FUD and/or misunderstanding on your part.
"data=ordered" is ext3/4's name for "don't expose stale data on a crash," something which XFS has never done, with or without a mount option. ext3/4 also have "data=writeback" which means "DO expose stale data on a crash." XFS does not need feature parity for ill-advised options.
Any filesystem will lose buffered and unsynced file data on a crash (http://lwn.net/Articles/457667/). XFS has made filesystem integrity and data persistence job one since before ext3 existed. Like any filesystem, it has had bugs, but implying that it was unsafe for use until recently is incorrect.
I say this as someone who's been working on ext3, ext4 and xfs code for over a decade, combined.
Re:Read their website (Score:5, Informative)
Every file system is/should be labled "experimental" in a way. The long answer from the btrfs FAQ is pretty good, and makes some sense:
Long answer: Nobody is going to magically stick a label on the btrfs code and say "yes, this is now stable and bug-free". Different people have different concepts of stability: a home user who wants to keep their ripped CDs on it will have a different requirement for stability than a large financial institution running their trading system on it. If you are concerned about stability in commercial production use, you should test btrfs on a testbed system under production workloads to see if it will do what you want of it. In any case, you should join the mailing list (and hang out in IRC) and read through problem reports and follow them to their conclusion to give yourself a good idea of the types of issues that come up, and the degree to which they can be dealt with. Whatever you do, we recommend keeping good, tested, off-system (and off-site) backups.
Re:Happy with XFS (Score:2, Informative)
there's CXFS which _is_ a clustered filesystem. Not as popular as GFS or OCFS2, but it's there, and uses the same block format as 'regular' XFS.
Not sure what you refer by "mature OS", but note that ZFS is _not_ a cluster filesystem by any strecth of the definition.
Re:Read their website (Score:5, Informative)
He said the only FS that fit-the-bill was ZFS. His team could not find an enterprise company that stored at least 1PB of data on ZFS and had a non-user caused critical problem within the past 5 years. That was many years ago and he has not had a single issue with his multi-PB storage that is being used by hundreds of departments.
ZFS is not perfect, but it sets a very high bar.
Re:Read their website (Score:5, Informative)
Re:Happy with XFS (Score:4, Informative)
Ever heard of the sync command?
Re:Read their website (Score:2, Informative)
Mirrors and snapshots are not backups. They can be used to create backups, but are not backups in themselves.
Re:Happy with XFS (Score:5, Informative)
So, until your understand this basic idea, don't go claiming you know _ANYTHING_ about filesystems.
Without sounding like too much of a jerk, I have hundreds of commits in the linux-2.6 fs/* tree. This is what I do for a living. :)
I actually do have a pretty decent grasp of how Linux journaling filesystems behave.
Test your assumptions on ext4 with default mount options. Create a new file and write some buffered data to it, wait 5-10 seconds, punch the power button, and see what you get. (You'll get a 0 length file) Or write a pattern to a file, sync it, overwrite with a new pattern, and punch power. (You'll get the old pattern). Or write data to a file, sync it, extend it, and punch power. (You'll get the pre-extension size). Wait until the kernel pushes data out of the page cache to disk, *then* punch power, and you'll get everything you wrote, obviously.
XFS and ext4 behave identically in all these scenarios. Maybe you can show me a testcase where XFS misbehaves in your opinion? (bonus points for demonstrating where XFS actually fails any posix guarantee).
Yes, ext3/4 have data=journaled - but its not default, and with ext4, that option disables delalloc and O_DIRECT capabilities. 99% of the world doesn't run that way; it's slower for almost all workloads and TBH, is only lightly tested.
Yes, ext3's data=ordered pushes out tons of file data on every journal commit. That has serious performance implications, but it does shorten the window for buffered data loss to the journal commit time.
You want data persistence with a posix filesystem? Use the proper data integrity syscalls, that's all there is to it.
Re:Read their website (Score:2, Informative)
I'm sorry, but I call BS on this. I love ZFS and it is a great ,solid file system. But your friend couldn't have gone looking for case studies of five-year-plus ZFS usage "many years ago". ZFS has only been around for about eight years, the first few of those years it saw very limited usage (ie OpenSolaris). Yes, ZFS is a great file system, but let's stick to factual reasons why it is good, no need to make up stories.