josefbacik

6 ms·

1.
by josefbacik 1y ago
I’m framing this comment and putting it on my wall in my office.
2.
by josefbacik 7y ago
Keep in mind most of us don’t use our @fb.com addresses. LWN keeps track of companies by keeping track of who works where so our numbers are much higher than this list shows.
3.
by josefbacik 7y ago
Agreed, drive managed is far better from a usability standpoint.
4.
by josefbacik 7y ago
Host managed also means messing with the file system, and the patch set for btrfs is not small. Plus you have to disable a bunch of features (like preallocation since you can’t move the write pointer backwards) which is going to surprise p
5.
by josefbacik 7y ago
Not sure what you are talking about, it’s definitely endian neutral. You can’t take different page sized fs and put it on another page size arch, but that’s a separate issue.
6.
by josefbacik 7y ago
Cause it’s a summit to talk about the whole ecosystem, not one file system. We btrfs developers talk enough to each other, we don’t need to bore the rest of the attendees with our own topics. That’s what the hallway tracks are for. I put
7.
by josefbacik 8y ago
It would be nice, but for complicated systems in the kernel you sometimes have to provide evidence that the old way sucks and the new way is better. With this work we can easily point at our production workloads and say the in kernel oom k
8.
by josefbacik 9y ago
I spent an unreasonable amount of time working on grub2. The stuff I looked at the most where the uefi spec http://wiki.phoenix.com/wiki/index.php/Category:UEFI And then the uefi stub code in the Linux kernel, as
9.
by josefbacik 9y ago
Lol what? We don't ship code that isn't upstream. It sucks to maintain and rebase if you have a shitton of proprietary patches. Everything we do with the kernel is open source, you wouldn't be able to hire kernel developer
10.
by josefbacik 9y ago
Facebook is using it for lots of shit. Chroots for containers because we can easily snapshot them and use them. Use it for build testing, so snapshot base repo, checkout commit, build, throw away. Gluster which takes huge backups and the
11.
by josefbacik 9y ago
A Linux file system developer in theory, a "this is broken and is in/related to the kernel" developer in practice.
12.
by josefbacik 9y ago
Sendfile isn't async, it just avoids the user space copy, and in some cases the copy from the fd to the socket. Aio doesn't require xfs, just O_DIRECT, which can be tricky to get right and more work than userspace guys want to de
13.
by josefbacik 9y ago
All this talk about Oracle is just plain stupid. Oracle doesn't control anything, the community does. One core developer still works on Btrfs from Oracle, the vast majority of the contributions come from outside Oracle. Now as to &gt
14.
by josefbacik 9y ago
Nope I love Red Hat and loved working for Red Hat and still interact with most of my colleagues there on a day to day basis. I shouldn't be speaking for everybody, but from what I can tell we're all pretty happy where we are, so
15.
by josefbacik 9y ago
They brought on Zach right before I left specifically to help with the effort, but he left as well. I can't really speak to Red Hat's overall strategic decisions, but really they have a large local file system team, and a lot of
16.
by josefbacik 9y ago
People are making a bigger deal of this than it is. Since I left Red Hat in 2012 there hasn't been another engineer to pick up the work, and it is _a lot_ of work. For RHEL you are stuck on one kernel for an entire release. Every fix
17.
by josefbacik 10y ago
Or I just mistyped and you are reading in too much to it?
18.
by josefbacik 10y ago
Systemtap was fantastic, but super finnicky. You had to have debuginfo for the kernel installed plus the source. This was fine for RHEL but kind of a pain elsewhere. Then you run into other problems like sometimes the distro compiler was
19.
by josefbacik 10y ago
You are confusing hardlinks with symlinks. They are similar but not the same. Symlinks in Linux most certainly get their own inode and can contain data blocks.
20.
by josefbacik 10y ago
Symlinks are implemented as files in Linux, we write the path into the file that you are pointing to, so there most certainly is data that must be fsync()'ed if you want it to be persistent. Edit: If you want to fsync the symlink you c
21.
by josefbacik 10y ago
The rename is atomic, the data being in the file is the problem, there is no garuntee unless you fsync.
22.
by josefbacik 10y ago
This is just an accident of how some file systems are implemented and isn't actually garunteed. If you did this on xfs you could still end up with the a 0 length symlink if you crashed at just the right time.
23.
by josefbacik 10y ago
We have to look up the physical extent in the extent reference tree, so the cost is independent of the number of snapshots and more a function of the fragmentation of the extent tree. The metadata is all cached of course, but fragmentation
24.
by josefbacik 10y ago
Yeah nocow only works if there are no snapshots, which is why we have to check, so if you use snapshots it falls back to COW.
25.
by josefbacik 10y ago
No it doesn't.
26.
by josefbacik 10y ago
Not sure how that tracks. These file systems are huge code bases with lots of problems and areas for improvement. When you only have 2-4 people who understand most of it at a given time things move slowly. If I could tell somebody to go
27.
by josefbacik 10y ago
ZFS has a 7 year head start on BTRFS and has traditionally had about 5 times as many core contributors at any given time so I imagine they've solved this in some novel way by now.
28.
by josefbacik 10y ago
NOCOW is horribly expensive because we still have to go check and make sure that there are no snapshots pointing at the changing extents. It only solves the fragmentation issue, and if you don't prealloc your image it doesn't even
29.
by josefbacik 10y ago
There are no docs. I'm not a qcow2 expert, what I know is very basic so anything I say about qcow2 can be very wrong. So qcow has a read only base image that gets updated when we change things. The image format just had the changes f
30.
by josefbacik 10y ago
It's a general purpose file system, it does great with metadata heavy workloads and normal streaming writes. The overwrite case is special because of COW. Eventually we'll be comparable to everybody else but we aren't now.

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