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The State of ZFS on Linux

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Re: The State of ZFS on Linux

#11

Post by ryao »

agapon wrote: post #4

Great blog post! Something from personal experience. OpenZFS on FreeBSD feels mostly like a port of illumos ZFS where most of the non-FreeBSD-specific changes happen in illumos and then get ported downstream. On the other hand, OpenZFS on Linux feels like a fork. There is certainly a stream of changes from illumos, but there's a rather non-trivial amount of changes to the core code that happen in ZoL.

This is because Martin Matuška of FreeBSD has been focused on upstreaming changes made in FreeBSD's ZFS port into Illumos. At present, the ZFSOnLinux project has had no one dedicated to that task and code changes mostly flow from Illumos to Linux. This is starting to change. A small change went upstream to Illumos earlier this year and more should follow in the future.

That being said, there are commonalities between Illumos and FreeBSD that make it easier for the FreeBSD ZFS developers to collaborate with their Illumos counterparts:

1. FreeBSD and Illumos have large kernel stacks (4 pages and 6 pages respectively) while Linux's kernel stacks are limited to 2 pages.

2. In-kernel virtual memory is well supported in FreeBSD and Illumos while Linux's in-kernel virtual memory is crippled for philosophical reasons.

3. FreeBSD and Illumos have both the kernel and userland in the same tree. FreeBSD even maintained Illumos' directory structure in its import of the code while ZoL's project lead decided to refactor it to be more consistent with Linux.

Difficulties caused by these differences should go away changes made in ZoL to improve code portability are sent back to Illumos.

Re: The State of ZFS on Linux

#12

Post by ryao »

IgorPartola wrote: post #6
a2743906 wrote: post #5

I'm using ZFS right now, because I need something that cares for data integrity, but the fact that it will never be included in Linux is a very big issue for me. Every time you upgrade your kernel, you have to upgrade the separate modules as well - this is the point where bad things can happen. I will definitely be looking into Btrfs once it is more reliable. For now I'm having a bit of a problem with SSD caching and…

Out of curiosity, what distro are you using that's giving you problems? My Ubuntu box is humming along with no problems: kernel and ZFS updates happen at the same time.

That is a feature of DKMS. Not all distributions use this, but most distributions on which ZFS is available have ways of avoiding this problem.

Re: The State of ZFS on Linux

#13

Post by ryao »

a2743906 wrote: post #5

I'm using ZFS right now, because I need something that cares for data integrity, but the fact that it will never be included in Linux is a very big issue for me. Every time you upgrade your kernel, you have to upgrade the separate modules as well - this is the point where bad things can happen. I will definitely be looking into Btrfs once it is more reliable. For now I'm having a bit of a problem with SSD caching and…

Which distribution are you using and does this involve / on ZFS? Most distributions have ways of avoiding this problem. If you are using a distribution where this is a problem, I would like to know so that I can try to address it. I can do nothing about it without knowing more.

Re: The State of ZFS on Linux

#14

Post by JeremyNT »

ryao wrote: post #2

I am the author. Feel free to respond with questions. I will be watching for questions throughout the day.

I very much adore ZoL. Thank you for your efforts. Everything critical works and works very well.

While I get the sense that this is probably not the focus of your own work, do you have any thoughts on the maturity of the "share" facilities when using ZoL, and as the project matures will these become more of a priority? These are "nice to have" features that are obviously of relatively low importance.

You mentioned shareiscsi is unimplemented, but I also find that its friends sharenfs and especially sharesmb have some rough edges as well. When I moved a pool from an OI machine to a Linux machine, I had to massage all of my share attributes to make them function.

Re: The State of ZFS on Linux

#15

Post by ryao »

ownedthx wrote: post #9

At a previous job, we built a proof-of-concept Sinatra service (i.e., HTTP/RESTful service) that would, on a certain API call, clone from a specified snapshot, and also create an iscsi target to that new clone. This was on OpenIndiana initially, then some other variant of that OS as a second attempt. The client making the HTTP request was IPXE; so, every time the machine booted, you'd get yourself a flesh clone + isc…

1. I am not aware of this specific issue. However, I am aware of an issue involving slow pool import with large numbers of zvols. Delphix has developed a fix for it that implements prefix. It should be merged into various Open ZFS platforms soon. It could resolve the problem that you describe.

2. Matthew Ahrens' synctask rewrite fixed this in Open ZFS. It took a while for the fix to propagate to tagged releases, but all Open ZFS platforms should now have it. ZoL gained it with the 0.6.3 release. Here is a link to a page with links to the commits that added this to each platform as well as the months in which the were added:

http://open-zfs.org/wiki/Features#synctask_rewrite

Re: The State of ZFS on Linux

#16

Post by blumentopf »

Nursie wrote: post #3
ryao wrote: post #2

I am the author. Feel free to respond with questions. I will be watching for questions throughout the day.

I don't really have a question, but as a ZoL user I'd just like to say thanks for all the hard work. It makes management of my disk arrays pretty painless and has some fantastic migration/recovery stuff going on. All of which I'm sure you know!

I use ZFS on a dual-boot Mac to cross-mount the Linux partitions on OS X. ZFS is pretty much the only file system that allows this: The XFS OSXFUSE plugin is read-only, the ext plugin only supports ext2 with unstable write support and BtrFS can't be mounted on OS X at all.

The ZoL-derived OpenZFSonOSX port inherits ZoL's maturity, runs in kernel space and the OS X integration is really nice (Notification Center integration in ZED, custom icons, etc).

Lovin' it!

Re: The State of ZFS on Linux

#17

Post by ryao »

JeremyNT wrote: post #14
ryao wrote: post #2

I am the author. Feel free to respond with questions. I will be watching for questions throughout the day.

I very much adore ZoL. Thank you for your efforts. Everything critical works and works very well. While I get the sense that this is probably not the focus of your own work, do you have any thoughts on the maturity of the "share" facilities when using ZoL, and as the project matures will these become more of a priority? These are "nice to have" features that are obviously of relatively low importance. You mentioned s…

You can obtain the commands that you used to massage your sharenfs and sharesmb settings from `zpool history`. Please file issues with them in the issue tracker:

https://github.com/zfsonlinux/zfs/issues/new

Please include information describing your distribution, the distribution release, your kernel version, the ZoL release and also the Samba version.

Re: The State of ZFS on Linux

#18

Post by ryao »

IgorPartola wrote: post #8
ryao wrote: post #2

I am the author. Feel free to respond with questions. I will be watching for questions throughout the day.

Is there a plan at some point to include a daemon or a cron job to run automatic zpool scrubbing? I believe this was a feature that is available in other OSs' packages, but not currently with ZoL. Currently, I include two cronjobs, like so: 18 * * * * /sbin/zpool list | grep ztank | grep ONLINE > /dev/null || /sbin/zpool status 35 1 * * 4 /sbin/zpool scrub ztank This way cron simply emails me if there are errors. How…

ZoL 0.6.3 introduced the ZFS Event Daemon. This functionality could likely be implemented into it. Please file an issue requesting this:

https://github.com/zfsonlinux/zfs/issues/new

Re: The State of ZFS on Linux

#19

Post by ryao »

IgorPartola wrote: post #7
Nursie wrote: post #3

Earlier quoted context omitted.

I don't really have a question, but as a ZoL user I'd just like to say thanks for all the hard work. It makes management of my disk arrays pretty painless and has some fantastic migration/recovery stuff going on. All of which I'm sure you know!

Seconded. ZFS is the only filesystem I trust with my children's baby pictures, as well as to store the git repo's for my personal projects (stuff I don't want on GitHub for a variety of reasons).

I am happy to hear that. While I certainly think ZFS is the best filesystem available for storing this kind of data, i would like to add a word of caution that ZFS is not a replacement for backups. I elaborated on this in one of the supplementary blog posts:

https://clusterhq.com/blog/file-systems-data-loss-zfs/#disk-...

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