Ubuntu 19.10 Indeed Working On "Experimental ZFS Option" In Ubiquity Installer

[roryrjb]

I'm not an expert on filesystems or anything, but it seems like certain people and companies are using Solaris/illumos and FreeBSD mainly for ZFS, if Canonical can integrate a stable ZFS implementation on Linux, that appears to me very significant.

[skeevy420]

I keep reading (on the internetz) that ZFS is not suitable for single disk setups (no fsck etc.), is this (still) true? Would that mean that for my laptop (single NVMe SSD), I should keep using e.g. btrfs for my root partition?

I've been using it on a 2TB single disk since the 0.6.2 days for all my Steam games and multimedia without any issues.

Single disk should be fine, I would be more worry eventually about memory requirements.
Actually, if you don't use ECC RAM would a raid 1 setup (and regular scrubs) help eventually bust bits flipping (bit rot)??

The memory usage can be tuned with the kernel command line.

zfs.zfs_arc_max=8589934592

That limits it to 8GB max. ZFS also releases its ram if the system needs it so limiting it really isn't necessary unless one has a bunch of ram and makes use of ram disks and such. If one knows a lot of their system's ram will be used for other things it makes sense to limit ZFS. For example, I have 48GB of ram, 24GB on a ram disk for compiling software and /tmp, and I limit ZFS to 8GB so I know that my system always has at least 16GB of system ram available for whatever tasks I might be doing. Even with my example, 8GB is too much because it's only a for a single 2TB HDD...but I have the ram to spare so I don't really give a damn...

I only use ECC ram these days so I haven't studied up ZFS w/o ECC. starshipeleven covered it pretty well in posts 6 and 7.

[Guest]

Will this push Oracle to sue? Canonical should at least inform of the fact that the ZoL module isn't GPL'd.

[starshipeleven]

Cache (ARC, Adaptive Replacement Cache) is on by default for ZFS, but it automatically drops memory usage in response to memory pressure on the system. The only memory hog on ZFS is deduplication.

I was thinking of L2ARC, which is not enabled by default.
Yes it's a feature where you add SSDs as cache, but RAM usage increases significantly when you do.

[Chugworth]

Hopefully Ubuntu's prominent use of ZFS will help to dispel the silly notion that licensing prevents it from being distributed with Linux.

[Niarbeht]

I was thinking of L2ARC, which is not enabled by default.
Yes it's a feature where you add SSDs as cache, but RAM usage increases significantly when you do.

No it doesn't. L2ARC needs a little bit of RAM to store the metadata for the blocks stored on disk, but you'd need a f***ing HUGE L2ARC for it to matter.

[starshipeleven]

No it doesn't. L2ARC needs a little bit of RAM to store the metadata for the blocks stored on disk, but you'd need a f***ing HUGE L2ARC for it to matter.

Ah crap I forgot that ZFS users on Lunix (tm) use a 128k block size.

L2ARC eats 400bytes per block so the total consumption depends from the block size.

On FreeNAS the default is 16k or 8k, for each 100GB of SSD L2ARC you need like 2.5GB or 5GB respectively. That's kind of significant. With 128k block size it's negligible.

[starshipeleven]

Hopefully Ubuntu's prominent use of ZFS will help to dispel the silly notion that licensing prevents it from being distributed with Linux.

What the license is preventing is upstreaming ZFS in Linux kernel, distribution as a downstream module is fine.

[k1e0x]

This is cool. Nice job Ubuntu.

Some people asked questions so..

Is ZFS fine for single disk, ssd, desktop/laptops? = Yes
Why would you do this? Same reason you'd use ZFS on any other system. Reliability, integrity, ease of management and it's feature set. Perhaps you have another system or a FreeNAS box and you want to use ZFS send and receive from cron to maintain your backups. Or you are worried about bad data and corrupt files finding their way into your backups silently. ZFS will actually tell you. "I can't read this, so go restore your backup. It's dead Jim." Instead of happy backing up the bad file like most file systems. The con to this is it can be a little slower than EXT4 (tho not too bad see the memory part) - ZFS also has trim in Linux now (FreeBSD has had this for some time) Note: if you do want to use ZFS cross OS, you want to make sure you create compatible pools, by default they may not be.

Do I need a ton of ECC ram to run ZFS? = No
ZFS is no better or worse than any other file system when you have memory corruption. Sun made this recommendation to enterprises with ZFS's release back in 2005 and it's just stuck around.. It was never really right and bad info never dies. (note: when you are reading documentation on ZFS, look for current stuff on ZoL or FreeBSD's version and NOT Oracles) - ZFS uses it's own memory manager on Linux and I have found that sometimes when the system comes under memory pressure Linux likes to try to swap programs out before ZFS frees it's ARC cache. It causes ZFS to eat up more memory. You can limit the size of the ZFS ARC as people have said but a better solution is just to tune Linux to not swap unless it absolutely has to and set sysctl vm.swappiness=5 As that seems to give very smooth snappy performance.

License omg panic FUD! = lol
The GPL applies to distribution not users. As a user you can do whatever you want with your own system. What Canonical is doing is perfectly fine and no different than what every distro does with the closed source Nvidia drivers. Nobody seems to have a problem with that. It's just a module that you add to the kernel to make it work. At least ZFS is actually open source and free code (unlike all those other binary blobs you are running that you're *not* complaining about.)

[AndyChow]

For someone a bit out of the loop, is ZFS on Linux well integrated, reliable and has good performance?

I know (and have used) ZFS on FreeBSD, so I see why you might want to use it with Linux as well, but last I read about it, it was described as not very well integrated in the Linux system.

It's actually now the opposite. ZOL (ZFS on linux) is used as baseline for ZFS on FreeBSD. https://lists.freebsd.org/pipermail/...er/027085.html

So ZFS is now better integrated on linux than BSD.