# ZFS Configuration This text deals with specific ZFS configuration questions for Ansible-NAS. If you are new to ZFS and are looking for the big picture, please read the [ZFS overview](zfs_overview.md) introduction first. ## Just so there is no misunderstanding Unlike other NAS variants, Ansible-NAS does not install, configure or manage the disks or file systems for you. It doesn't care which file system you use - ZFS, Btrfs, XFS or EXT4, take your pick. Nor does it provides a mechanism for snapshots or disk monitoring. As Tony Stark said to Loki in _Avengers_: It's all on you. However, Ansible-NAS has traditionally been used with the powerful ZFS filesystem. Since out of the box support for [ZFS on Linux](https://zfsonlinux.org/) with Ubuntu is comparatively new, this text shows how to set up a simple storage configuration. To paraphrase Nick Fury from _Winter Soldier_: We do share. We're nice like that. > Using ZFS for Docker containers is currently not covered by this document. See > [the official Docker ZFS > documentation](https://docs.docker.com/storage/storagedriver/zfs-driver/) > instead. ## The obligatory warning We take no responsibility for any bad thing that might happen if you follow this guide. We strongly suggest you test these procedures in a virtual machine first. Always, always, always backup your data. ## The basic setup For this example, we're assuming two identical spinning rust hard drives for Ansible-NAS storage. These two drives will be **mirrored** to provide redundancy. The actual Ubuntu system will be on a different drive and is not our concern. > [Root on ZFS](https://github.com/zfsonlinux/zfs/wiki/Ubuntu-18.04-Root-on-ZFS) > is still a hassle for Ubuntu. If that changes, this document might be updated > accordingly. Until then, don't ask us about it. The Ubuntu kernel is already ready for ZFS. We only need the utility package which we install with `sudo apt install zfsutils`. ### Creating a pool We assume you don't mind totally destroying whatever data might be on your two storage drives, have used a tool such as `gparted` to remove any existing partitions, and have installed a new GPT partition table on each drive. To create our ZFS pool, we will use a command in this form: ``` sudo zpool create -o ashift= mirror ``` The options from simple to complex are: **NAME**: ZFS pools traditionally take their names from characters in the [The Matrix](https://www.imdb.com/title/tt0133093/fullcredits). The two most common are `tank` and `dozer`. Whatever you use, it should be short - think `ash`, not `xenomorph`. **DRIVES**: The Linux command `lsblk` will give you a quick overview of the hard drives in the system. However, we don't pass the drive specification in the format `/dev/sde` because this is not persistent. Instead, [always use](https://github.com/zfsonlinux/zfs/wiki/FAQ#selecting-dev-names-when-creating-a-pool) the output of `ls /dev/disk/by-id/` to find the drives' IDs. **ASHIFT**: This is required to pass the [sector size](https://github.com/zfsonlinux/zfs/wiki/FAQ#advanced-format-disks) of the drive to ZFS for optimal performance. You might have to do this by hand because some drives lie: Whereas modern drives have 4k sector sizes (or 8k for many SSDs), they will report 512 bytes because Windows XP [can't handle 4k sectors](https://support.microsoft.com/en-us/help/2510009/microsoft-support-policy-for-4k-sector-hard-drives-in-windows). ZFS tries to [catch the liars](https://github.com/zfsonlinux/zfs/blob/master/cmd/zpool/zpool_vdev.c) and use the correct value. However, this sometimes fails, and you have to add it by hand. The `ashift` value is a power of two, so we have **9** for 512 bytes, **12** for 4k, and **13** for 8k. You can create a pool without this parameter and then use `zdb -C | grep ashift` to see what ZFS generated automatically. If it isn't what you think, destroy the pool again and add it manually. In our pretend case, we use two 3 TB WD Red drives. Listing all drives by ID gives us something like this, but with real serial numbers: ``` ata-WDC_WD30EFRX-68EUZN0_WD-WCCFAKESN01 ata-WDC_WD30EFRX-68EUZN0_WD-WCCFAKESN02 ``` WD Reds have a 4k sector size. The actual command to create the pool would then be: ``` sudo zpool create -o ashift=12 tank mirror ata-WDC_WD30EFRX-68EUZN0_WD-WCCFAKESN01 ata-WDC_WD30EFRX-68EUZN0_WD-WCCFAKESN02 ``` Our new pool is named `tank` and is mirrored. To see information about it, use `zpool status tank` (no `sudo` necessary). If you screwed up (usually with `ashift`), use `sudo zpool destroy tank` and start over _now_ before it's too late. ### Pool and filesystem properties Pools have properties that apply either to the pool itself or to filesystems created in the pool. You can use the command `zpool get all tank` to see the pool properties and `zfs get all tank` to see the filesystem properties. Most default values are perfectly sensible, some you'll [want to change](https://jrs-s.net/2018/08/17/zfs-tuning-cheat-sheet/). Setting defaults makes life easier when we create our filesystems. ``` sudo zpool set autoexpand=on tank sudo zfs set atime=off tank sudo zfs set compression=lz4 tank ``` `autoexpand=on` lets the pool grow when you add larger hard drives. `atime=off` means that your system won't update a time stamp every time a file is accessed, something which would use a lot of resources. Usually, you don't care. Compression is a no-brainer on modern CPUs and should be on by default (we will discuss exceptions for compressed media files later). ## Creating filesystems To actually store the data, we need filesystems (also known as "datasets"). For our very simple default Ansible-NAS setup, we will create two: One filesystem for movies (`movies_root` in `all.yml`) and one for downloads (`downloads_root`). ### Movies (and other large, pre-compressed files) We first create the basic filesystem: ``` sudo zfs create tank/movies ``` Movie files are usually rather large, already in a compressed format and for security reasons, the files stored there shouldn't be executable. We change the properties of the filesystem accordingly: ``` sudo zfs set recordsize=1M tank/movies sudo zfs set compression=off tank/movies sudo zfs set exec=off tank/movies ``` The **recordsize** here is set to the currently largest possible value [to increase performance](https://jrs-s.net/2019/04/03/on-zfs-recordsize/) and save storage. Recall that we used `ashift` during the creation of the pool to match the ZFS block size with the drives' sector size. Records are created out of these blocks. Having larger records reduces the amount of metadata that is required, because various parts of ZFS such as caching and checksums work on this level. **Compression** is unnecessary for movie files because they are usually in a compressed format anyway. ZFS is good about recognizing this, and so if you happen to leave compression on as the default for the pool, it won't make much of a difference. [By default](https://zfsonlinux.org/manpages/0.7.13/man8/zfs.8.html#lbAI), ZFS stores pools directly under the root directory. Also, the filesystems don't have to be listed in `/etc/fstab` to be mounted. This means that our filesystem will appear as `/tank/movies` if you don't change anything. We need to change the line in `all.yml` accordingly: ``` movies_root: "/tank/movies" ``` You can also set a traditional mount point if you wish with the `mountpoint` property. Setting this to `none` prevents the file system from being automatically mounted at all. The filesystems for TV shows, music files and podcasts - all large, pre-compressed files - should probably take the exact same parameters. ### Downloads For downloads, we can leave most of the default parameters the way they are. ``` sudo zfs create tank/downloads sudo zfs set exec=off tank/downloads ``` The recordsize stays the 128 KB default. In `all.yml`, the new line is ``` downloads_root: "/tank/downloads" ``` ### Other data Depending on the use case, you might want to create and tune more filesystems. For example, [Bit Torrent](http://open-zfs.org/wiki/Performance_tuning#Bit_Torrent), [MySQL](http://open-zfs.org/wiki/Performance_tuning#MySQL) and [Virtual Machines](http://open-zfs.org/wiki/Performance_tuning#Virtual_machines) all have known best configurations. ## Setting up scrubs On Ubuntu, scrubs are configured out of the box to run on the second Sunday of every month. See `/etc/cron.d/zfsutils-linux` to change this. ## Email notifications To have the [ZFS demon](http://manpages.ubuntu.com/manpages/bionic/man8/zed.8.html) `zed` send you emails when there is trouble, you first have to [install an email agent](https://www.reddit.com/r/zfs/comments/90prt4/zed_config_on_ubuntu_1804/) such as postfix. In the file `/etc/zfs/zed.d/zed.rc`, change the three entries: ``` ZED_EMAIL_ADDR= ZED_NOTIFY_INTERVAL_SECS=3600 ZED_NOTIFY_VERBOSE=1 ``` If `zed` is not enabled, you might have to run `systemctl enable zed`. You can test the setup by manually starting a scrub with `sudo zpool scrub tank`. ## Snapshots Snapshots create a "frozen" version of a filesystem, providing a safe copy of the contents. Correctly configured, they provide good protection against accidental deletion and certain types of attacks such as ransomware. On copy-on-write (COW) filesystems such as ZFS, they are cheap and fast to create. It is very rare that you _won't_ want snapshots. > Snapshots do not replace the need for backups. Nothing replaces the need for > backups except more backups. ### Managing snapshots by hand If you have data in a filesystem that never or very rarely changes, it might be easiest to just take a snapshot by hand after every major change. Use the `zfs snapshot` command with the name of the filesystem combined with an identifier separated by the `@` sign. Traditionally, this somehow includes the date of the snapshot, usually in some variant of the [ISO 8601](https://en.wikipedia.org/wiki/ISO_8601) format. ``` zfs snapshot tank/movies@2019-04-24 ``` To see the list of snapshots in the system, run ``` zfs list -t snapshot ``` To revert ("roll back") to the previous snapshot, use the `zfs rollback` command. ``` zfs rollback tank/movies@2019-04-24 ``` By default, you can only roll back to the most recent snapshot. Anything before then requires trickery outside the scope of this document. Finally, to get rid of a snapshot, use the `zfs destroy` command. ``` zfs destroy tank/movies@2019-04-24 ``` > Be **very** careful with `destroy`. If you leave out the snapshot identifier > and only list the filesystem - in our example, `tank/movies` - the filesystem > itself will immediately be destroyed. There will be no confirmation prompt, > because ZFS doesn't believe in that sort of thing. ### Managing snapshots with Sanoid Usually, you'll want the process of creating new and deleting old snapshots to be automatic, especially on filesystems that change frequently. One tool for this is [sanoid](https://github.com/jimsalterjrs/sanoid/). There are various instructions for setting it up, the following is based on notes from [SvennD](https://www.svennd.be/zfs-snapshots-of-proxmox-using-sanoid/). For this example, we'll assume we have a single dataset `tank/movies` that holds, ah, movies. First, we install sanoid to the `/opt` directory. This assumes that Perl itself is already installed. ``` sudo apt install libconfig-inifiles-perl libcapture-tiny-perl cd /opt sudo git clone https://github.com/jimsalterjrs/sanoid ``` It is probably easiest to link sanoid to `/usr/sbin`: ``` sudo ln /opt/sanoid/sanoid /usr/sbin/ ``` Then we need to setup the configuration files. ``` sudo mkdir /etc/sanoid sudo cp /opt/sanoid/sanoid.conf /etc/sanoid/sanoid.conf sudo cp /opt/sanoid/sanoid.defaults.conf /etc/sanoid/sanoid.defaults.conf ``` We don't change the defaults file, but it has to be copied to the folder anyway. Next, we edit the `/etc/sanoid/sanoid.conf` configuration file in two steps: We design the "templates" and then tell sanoid which filesystems to use it on. The configuration file included with sanoid contains a "production" template for filesystems that change frequently. For media files, we assume that there is not going to be that much change from day-to-day, and especially there will be very few deletions. We use snapshots because this provides protection against cryptolocker attacks and against accidental deletions. > Again, snapshots, even lots of snapshots, do not replace backups. For our example, we configure for two hourly snapshots (against "oh crap" deletions), 31 daily, one monthly and one yearly snapshot. ``` [template_media] frequently = 0 hourly = 2 daily = 31 monthly = 1 yearly = 1 autosnap = yes autoprune = yes ``` That might seem like a bunch of daily snapshots, but remember, if nothing has changed, a ZFS snapshot is basically free. Once we have an entry for the template, we assign it to the filesystem. ``` [tank/movies] use_template = media ``` Finally, we edit `/etc/crontab` to run sanoid every five minutes: ``` */5 * * * * root /usr/sbin/sanoid --cron ``` After five minutes, you should see the first snapshots (use `zfs list -t snapshot` again). The list will look something like this mock example: ``` NAME USED AVAIL REFER MOUNTPOINT tank/movies@autosnap_2019-05-17_13:55:01_yearly 0B - 1,53G - tank/movies@autosnap_2019-05-17_13:55:01_monthly 0B - 1,53G - tank/movies@autosnap_2019-05-17_13:55:01_daily 0B - 1,53G - ``` Note that the snapshots use no storage, because we haven't changed anything. This is a very simple use of sanoid. Other functions include running scripts before and after snapshots, and setups to help with backups. See the included configuration files for examples.