Annotation of wikisrc/zfs.mdwn, revision 1.20

1.1       gdt         1: # ZFS on NetBSD
                      2: 
1.11      gdt         3: This page attempts to do two things: provide enough orientation and
1.13      wiz         4: pointers to standard ZFS documentation for NetBSD users who are new to
1.11      gdt         5: ZFS, and to describe NetBSD-specific ZFS information.  It is
1.1       gdt         6: emphatically not a tutorial or an introduction to ZFS.
                      7: 
                      8: Many things are marked with \todo because they need a better
                      9: explanation, and some have question marks, indicating that the
                     10: statement needs verification.
                     11: 
                     12: # Documentation Pointers
                     13: 
                     14: See the man pages for zfs(8) and zpool(8).
                     15: 
1.4       gdt        16:   - [Oracle ZFS Administration Manual](https://docs.oracle.com/cd/E26505_01/html/E37384/index.html)
                     17:   - [FreeBSD Handbook ZFS Chapter](https://www.freebsd.org/doc/handbook/zfs.html)
1.14      gdt        18:   - [OpenZFS admin docs index page](https://github.com/openzfs/zfs/wiki/Admin-Documentation)
1.1       gdt        19: 
                     20: # Status of ZFS in NetBSD
                     21: 
1.12      gdt        22: ## Sources
                     23: 
                     24: \todo Verify/fix.
                     25: 
                     26: Currently, there are multiple ZFS projects/codebases:
                     27: 
                     28:   - ZFS as released under the CDDL (common ancestor)
                     29:   - [OpenZFS](http://www.open-zfs.org/wiki/Main_Page)
                     30:   - [zfsonlinux](https://zfsonlinux.org/)
                     31:   - proprietary ZFS in Solaris (not relevant in open source)
                     32: 
                     33: OpenZFS is a coordinating project to align open ZFS codebases.  There
                     34: is a notion of a shared core codebase and OS-specific adaptation code.
                     35: 
1.16      gdt        36: See [FreeBSD's history](https://wiki.freebsd.org/ZFSTuningGuide).
1.14      gdt        37: 
1.15      gdt        38: \todo Explain the relationship between OpenZFS and zfsonlinux.
                     39: 
1.12      gdt        40: ## NetBSD code history
                     41: 
                     42: \todo This section really needs help.
                     43: 
                     44: Before NetBSD 8, NetBSD imported ZFS code from ?
                     45: 
                     46: Before NetBSD 9, NetBSD imported updated ZFS code from FreeBSD.  That
                     47: FreeBSD code came from ?
1.1       gdt        48: 
                     49: ## NetBSD 8 and earlier
                     50: 
                     51: While there is some ZFS code, it is old, and seems to have significant
                     52: problems.  If one wants to use ZFS, first upgrade to NetBSD 9.  It is
                     53: unlikely that anyone is interested in helping, other than telling you
                     54: to upgrade to 9.
                     55: 
1.13      wiz        56: (Reports of how well NetBSD 8 works are welcome on netbsd-users, if it
1.1       gdt        57: can actually be recommended for use.)
                     58: 
                     59: ## NetBSD 9
                     60: 
                     61: There have been fixes since 9.0 RELEASE.  It is best to upgrade along
1.12      gdt        62: the netbsd-9 branch, but the release should be ok.  Most aspects work solidly.
1.1       gdt        63: 
1.12      gdt        64: \todo Explain this in terms of versions of FreeBSD OpenZFS and/or
                     65: zfsonlinux.
1.1       gdt        66: 
                     67: \todo This supports pool version 28/5000 (really true?).  Of the
                     68: feature flags found in modern OpenZFS, \todo are supported.
                     69: 
1.7       gdt        70: Generally, fixes to ZFS in current will be pulled up to 9, but new
1.5       gdt        71: features typically will not be.
                     72: 
1.1       gdt        73: ## NetBSD current
                     74: 
1.5       gdt        75: The ZFS code in current is very similar to that in 9.
                     76: 
1.9       gdt        77: There is initial support for [[ZFS root|wiki/RootOnZFS]], via booting from
1.5       gdt        78: ffs and pivoting.
1.1       gdt        79: 
1.14      gdt        80: One can make a ccd using a zvol as a component.  See the zvol section below.
1.1       gdt        81: 
1.16      gdt        82: ## Things that aren't supported yet
1.1       gdt        83: 
1.8       gdt        84: \todo hotswap (maybe - not clear exactly what this means)
1.1       gdt        85: 
1.13      wiz        86: \todo direct boot into zfs root (via boot blocks reading zfs)
1.1       gdt        87: 
                     88: ## Architectures
                     89: 
                     90: Most people seem to be using amd64.
                     91: 
                     92: To build zfs, one puts MKZFS=yes in mk.conf.  This is default on amd64
                     93: and aarch64 on netbsd-9.  In current, it is also default on sparc64.
                     94: 
                     95: More or less, zfs can be enabled on an architecture when it is known
                     96: to build and run reliably.  (Of course, users are welcome to build it
                     97: and report.)
                     98: 
                     99: # NetBSD-specific information
                    100: 
                    101: ## rc.conf
                    102: 
                    103: The main configuration is to put zfs=YES in rc.conf, so that the rc.d
1.13      wiz       104: scripts bring up ZFS and mount ZFS file systems.
1.1       gdt       105: 
1.14      gdt       106: ## pool locations
                    107: 
                    108: One can add disks or parts of disks into pools.  Methods of specifying
                    109: areas to be included include:
                    110: 
                    111:   - entire disks (e.g., /dev/rwd0d on amd64)
                    112:   - disklabel partitions (e.g., /dev/sd0e)
                    113:   - wedges (e.g., /dev/dk0)
                    114: 
1.6       gdt       115: ## legacy vs ? mount points
                    116: 
                    117: \todo Explain, if this is NetBSD specific.  Explain consequences, as
                    118: this seems to have something to do with mount ordering.
                    119: 
1.1       gdt       120: ## mount order
                    121: 
1.13      wiz       122: NetBSD 9 mounts other file systems and then ZFS file systems.  This can
1.3       gdt       123: be a problem if /usr/pkgsrc is on ZFS and /usr/pkgsrc/distfiles is on
                    124: NFS.  A workaround is to use noauto and do the mounts in
                    125: /etc/rc.local.
                    126: 
                    127: NetBSD current after 20200301 mounts ZFS first. \todo Explain
                    128: consequences.
1.1       gdt       129: 
1.19      gdt       130: ## NFS
                    131: 
                    132: \todo Verify if this is accurate.
                    133: 
                    134: zfs filesystems can be exported over NFS.  While there are zfs
                    135: commands that appear to be about controlling exports, they simply
                    136: print information that can be added to exports(5).
                    137: 
1.20    ! gdt       138: This is reported to work on 9.0 STABLE, but to cause a panic on
        !           139: current (20200302).
        !           140: 
1.14      gdt       141: ## zvol
                    142: 
                    143: Within a ZFS pool, the standard approach is to have file systems, but
                    144: one can also create a zvol, which is a block device of a certain size.
                    145: 
                    146: \todo The zvol will appear as /dev/???? and can be used in many
                    147: respects like a slice.  However, the system will not read disklabels
                    148: and gpt labels from a zvol; in this respect it is more like a disklabel
                    149: partition or wedge than a disk drive.
                    150: 
                    151: \todo Explain that one can export a zvol via iscsi.
                    152: 
                    153: \todo Explain if one can swap on a zvol.
                    154: 
                    155: \todo Explain that one can use ccd to create a normal-looking disk
                    156: from a zvol.  This allows reading a GPT label from the zvol, which is
                    157: useful in case the zvol had been exported via iscsi and some other
                    158: system created a label.
                    159: 
1.1       gdt       160: ## TRIM
                    161: 
                    162: There is some notion of TRIM and zfs using it.
                    163: 
                    164: \todo Explain how this relates to NetBSD.
                    165: 
                    166: # Memory usage
                    167: 
                    168: Basically, ZFS uses lots of memory and most people run it on systems
                    169: with large amounts of memory.  NetBSD works well on systems with
                    170: comparatively small amounts of memory.  So a natural question is how
                    171: well ZFS works on one's VAX with 2M of RAM :-)
                    172: 
1.11      gdt       173: More seriously, one might ask if it is reasonable to run ZFS on a RPI3
1.1       gdt       174: with 1G of RAM, or even if it is reasonable on a system with 4G.
                    175: 
                    176: \todo Give ballpark level for minimum sane RAM, and the amount which
                    177: is cleanly enough.
                    178: 
1.10      gdt       179: For now, a good guess is that a 4G system with only 1T of disk is
1.18      gdt       180: probably ok, and that 1G is very likely not ok.
1.10      gdt       181: 
1.2       gdt       182: FreeBSD has some documentation about memory use.  There is a notion of
1.18      gdt       183: a minimum of 1G (used for ZFS), and using 1G for 1T of storage, and
                    184: more if deduplication is enabled.  FreeBSD considers all i386 systems
                    185: to be low memory; this appears to be a clue.
1.1       gdt       186: 
1.2       gdt       187: \todo Explain if the FreeBSD sysctl list applies, or if not what we
                    188: should do instead.
                    189: 
1.7       gdt       190:   - [FreeBSD low memory documentation](https://www.freebsd.org/doc/handbook/zfs-advanced.html)
1.1       gdt       191: 
                    192: # Interoperability with other systems
                    193: 
                    194: \todo Explain pool version and feature flags relationship to FreeBSD,
                    195: Linux, OpenIndiana/Illumos/?, and ?
                    196: 
1.18      gdt       197: \todo Explain how to configure a pool in terms of version/features for
                    198: use with particula other systems.
                    199: 
1.14      gdt       200: # Quick Start
                    201: 
                    202: See the [FreeBSD Quickstart
                    203: Guide](https://www.freebsd.org/doc/handbook/zfs-quickstart.html); only
                    204: the first item is NetBSD specific.
                    205: 
                    206:   - Put zfs=YES in rc.conf.
                    207: 
                    208:   - Create a pool as "zpool create pool1 /dev/dk0".
                    209: 
                    210:   - df and see /pool1
                    211: 
1.17      gdt       212:   - Really, read the FreeBSD docs and the other linked documentation above.

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