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Btrfs Is Getting There, But Not Quite Ready For Production
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."
Incompatible license prevents ZFS inclusion with the kernel. This is why Btrfs exists and explains Oracle's involvement with both.
These comments are my own and do not necessarily reflect the views or opinions of my employer or colleagues...
* Yes, they're a large corporation and right hand doesn't know what left hand does... but isn't this more like the index finger not knowing what the middle finger is doing?
Do you even lift?
These aren't the 'roids you're looking for.
No, using a file system that doesn't ship with the kernel makes things "not production ready." Licensing is the reason why it doesn't ship with the kernel, but it's not shipping with the kernel that keeps it out of critical production use.
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.
It _is_ quite reliable, even on the face of hardware failure.
Several years ago, I hit the 8TB limit of ext3 and had to migrate to a bigger filesystem. ext4 wasn't ready back then (and still today it's not easy to use on big volumes). Already had bad experiences with reiserfs (which was standard on SuSE), and the "you'll lose data"warnings on XFS docs made me nervous. It was obviously designed to work on very high-end hardware, which I couldn't afford.
so, I did extensive torture testing. hundreds of pull-the-plug situations, on the host, storage box and SAN switch, with tens of processes writing thousands of files on million-files directories. it was a bloodbath.
when the dust settled, ext3 was the best by far, managing to never lose more than 10 small files in the worst case, over 70% of the cases recovered cleanly. XFS was slightly worse, never more than 16 lost files and roughly 50% clean recoveries. ReiserFS was really bad, always losing more than 50-70 files and sometimes killing the volume. JFS didn't lose the volume, but lost files count never went below 130, sometimes several hundred.
needless to say, i switched to XFS, and haven't lost a single byte yet. and yes, there has been a few hardware failures that triggered scary rebuilding tasks, but completed cleanly.
-Kz-
Please mod parent informative.
One of the retarded things about btrfs is that you can not see how much disk space is being used by each subvolume. How the hell can you have a filesystem and not know how much space is in use or free ??
The design of ZFS is much more wholistic. That is, when we take a step back and look at both the micro and macro we see that we are really trying to solve 3 problems:
* Volume Management
* File System
* Data Integrity
ZFS solves all of these be leveraging knowledge from ALL the layers as one cohesive whole.
https://blogs.oracle.com/bonwick/en_US/entry/rampant_layering_violation
Why RAID is fundamentally broken
https://blogs.oracle.com/bonwick/entry/raid_z
Another interesting doc
http://www.scribd.com/doc/43973847/5/ZFS-Design-Principles
I tried btrfs as my main laptop filesystem:
nice features, speed ok, but i happened to unplug by mistake the power supply, without a battery. bad crash... I tried using btrfsck, and other debug tools, even in the "dangerdon'teveruse" git branch, they just segfaulted. at the end my filesystem was unrecoverable, I used btrfs-restore, only to find out that 90% of my files had been truncated to 0... even files i didn't use for months....
now, maybe it was the compress=lzo option, or maybe I played a little too much with the repair tools (possible), but untill btrfs can sustain power drops without problems, and the repair tools at least do not segfault, I won't use it for my main filesystem...
btrfs is supposed to save a consistent state every 30 seconds, so I don't understand how I messed up that bad.... maybe the superblock was gone and the btrfsck --repair borked everything, I don't know.... luckily for me: backups :)
"I was gratified to be able to answer promptly, and I did. I said I didn't know." -- Mark Twain
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.
Well, then your part of the problem. Your idea that you have to be correct or fast is sadly sort of wrong. Its possible to be correct without completely destroying performance. I have a few commits in the kernel as well mostly to fix completely broken behavior (my day job in the past was working on an enterprise unix). So, I do understand filesystems too. Lately, my job has been to replace all that garbage, from the scsi midlayer up, so that a small industry specific "application" can both make guarantees about the data being written to disk while still maintaining many GB/sec of IO. The result, actually makes the whole stack look really bad.
So, I'm sure your aware that on linux, if you use proper posix semantics (fsync() and friends) the performance is abysmal compared to the alternatives. This is mostly because of the "broken" fencing behavior (which has recently gotten better but still is far from perfect) in the block layer. Our changes depend on 8-10 year old features available in SCSI to make the guarantees that aren't available everywhere. But it penalizes devices which don't support modern tagging, ordering and fencing semantics rather than ones that do.
Generally in linux, application developers are stuck either dealing with orders of magnitude performance loss, or they have to play games in an attempt to second guess the filesystem. Neither is a good compromise and its sort of shameful.
Maybe its time to admit linux needs a filesystem that doesn't force people to choose either abysmal performance, or no guarantees about integrity.