• Welcome to Overclockers Forums! Join us to reply in threads, receive reduced ads, and to customize your site experience!

Zfs advice needed (Ubuntu)

Overclockers is supported by our readers. When you click a link to make a purchase, we may earn a commission. Learn More.


Mar 18, 2015
I currently use the second rig in my sig as "NAS + some other stuff" device. I have been reading on zfs and it seems like a fairly decent option that has alot to offer over other file systems. I currently use ext4 for almost everything that doesn't require a different fs.
Moving to zfs has me scratching my head a bit for a couple of reasons. The very most important is that my system is working as it is and "if it ain't broken don't fix it" is a good rule of thumb for myself and Linux :) The second is that I am not sure exactly how to proceed with the migration. Firstly I am using 14.04 and zfs isn't baked in until 16. 04. I've never done an upgrade over another OS with Linux but I do know that Windows is better off with a fresh install: is it the same on the Linux side? Should I do a fresh install of 16.04 or just install over 14.04? The other option, of course, is to add zfs to 14.04 and while I am not absolutely confident about it, it seems straight forward enough.
Once that question is answered I still have to decided on implementation, and do have questions about that, but I will wait to see what folks have to say about my other questions first. Thanks in advance :)
Not to send you away, but this is likely discussed in some fashion on the official Ubuntu forums if nobody here knows the answer immediately
Ubuntu forums are a strange beast for me personally, simply because I'm at a barely proficient level of knowledge and the questions are often rather specific. So unless someone has asked the exact same question it can be hard to extrapolate what I should do. That said, I often read so much that I never get to the task or so little that I botch the job, so that is fair advice for the Ubuntu forums :) I'm not in a huge hurry so I'll be able to cross reference responses from here and there for this one.
ZFS offers a lot of features desirable in a commercial storage environment:

ZFS is a combined file system and logical volume manager designed by Sun Microsystems. The features of ZFS include protection against data corruption, support for high storage capacities, efficient data compression, integration of the concepts of filesystem and volume management, snapshots and copy-on-write clones, continuous integrity checking and automatic repair, RAID-Z and native NFSv4 ACLs.

If the above would be what you envisioned for your home NAS then yea, ZFS would be of benefit; otherwise, like you mentioned, "if it ain't broken don't fix it" is a good rule of thumb".

There might be some uncertainties going the "upgrade" path, so moving to 16.04 would be quicker by doing a fresh install
So I have several comments so lets start with the "baked in" part.

While there is some higher level of integration with ZFS in 16.04, this is kind of a misnomer because there is still some level of effort to get ZFS up and going on 16.04, it isnt (yet) a first class file system.

Second I have been running ZFS on linux (CentOS 6 and Ubuntu 14.04) for multiple years now. I actually have a pool on Ubuntu that started as 4X2 tb then became 4x3TB and is currently sitting at 4x4TB drives. I have virtually no issues with ZFS on Ubuntu. This is our main media centre, if it stops working I have a very unhappy wife because it powers the "satellite" computers (nucs) which have kodi tied into the media and a mysql backend that live on the Ubuntu box.

I also have a CentOS box that has migrated from 1.5TB to 2TB and is currently sitting at 3TB (essentially when the media centre gets upgrades I pass down the disks to my CentOS box). I have had a few minor problems here, usually because DKMS seems to work a more reliably on Ubuntu. But really, nothing that I would use to discourage even the most novice linux user from using (if you are setting up ZFS, you have to have *some* base knowledge in the first place afterall)

So all that said, I wouldn't **** around with upgrading to 16.04 unless you really want to. For myself I probably will run 14.04 for at least another year before upgrading, my understanding is there have been some pretty significant bumps in 16.04 that need to get ironed out before I would consider upgrading a critical machine like this. In FACT I may wait until the end of 2017, then go to 16.04, then evaluate 18.04 and possibly jump up right away.

Its unclear how many disks you have and why you are considering ZFS. I use it as an alternative to standard raid 5, so I am looking for the parity bit and the error checking. If you have a small amount of data, and/or are not considering some sort of raid, I am not sure what benefit swapping out your filesystem would get you. Yes ZFS is great and has a lot of features, but is it enough to compel shifting all your data around so you can reformat your drives? Not sure about that one...

The other thing to consider is the ram requirement of ZFS, to my knowledge there is no real ram requirement for EXT or XFS file systems but ZFS is a copy-on-write file system so it has some hefty (in comparison) ram requirements, so know what you are getting into.

Ask your questions, I probably have answers to most of the questions you might have starting out
I have thought along the same lines for the 14.04/16.04 switch. I really see no reason to dump a working system for one of unknown strength - except for zfs being "baked in". My feeling was that the native support indicated less wrinkles so to speak. Having read your post I will go with my gut and get zfs working on 14.04 :)
Having said all that I don't believe a raid set up will be appropriate for my system as all the disks are quite different size (please correct if I am wrong). I have several empty TB that I have sitting in wait to be filled with media ( I plan a set up much like you said you had but with desktop satellites I stead of nuc). I'd only like to switch filesystems because I'd like to insure the integrity of my data ( which is a little over a TB as it sits now so better to switch now before the size grows) if I understand correctly I can start a pool with any/all of the unallocated space on my disks and move my data afterword. After that I can reformat the recently vacated partition and add it to the pool? That's really biggest question I have until I actually start installation of ZFS and I am still in the planning stages of this endeavor :)
Really while you *can* mix disks with ZFS, you shouldn't you are better to have either mirrored pools or raid-z than to throw a bunch of disks that are dis-similar in the same pool.

The golden rule of thumb is just because you *can* doesn't mean you should and that definitely applies here.

I would encourage you to map out your thoughts and designs and get input before disrupting a running system. For just having zfs on single disks remember that you should have at *lease* 20% of your hard disk free because it is copy-on-write (if you are not familiar with what this entails go look this up. You need to really understand what you are getting into). All this is not to scare you or discourage ZFS (I love it personally) but more to make sure you are making the right decision for the right reasons
LVM is your best bet for throughput, and stability by far. Zfs I would stay away from.

I could not disagree with this statement more adamantly (at least on the stability aspect). There is nothing wrong with LVM, but they are fundamentally solving different problems. While there is logical volume management in ZFS, it cares about data integrity where LVM doesn't give a monkey poop about the underlying disks, checksums or data integrity. With pure LVM, yes you can do snapshots, but you you are better to layer RAID and LVM, then just throwing a bunch of block devices in an LVM and hoping none of them die