Annotation of wikisrc/zfs.mdwn, revision 1.14

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: 
1.14    ! gdt        36: See [FreeBSD's history](https://wiki.freebsd.org/ZFSTuningGuide)
        !            37: 
1.12      gdt        38: ## NetBSD code history
                     39: 
                     40: \todo This section really needs help.
                     41: 
                     42: Before NetBSD 8, NetBSD imported ZFS code from ?
                     43: 
                     44: Before NetBSD 9, NetBSD imported updated ZFS code from FreeBSD.  That
                     45: FreeBSD code came from ?
1.1       gdt        46: 
                     47: ## NetBSD 8 and earlier
                     48: 
                     49: While there is some ZFS code, it is old, and seems to have significant
                     50: problems.  If one wants to use ZFS, first upgrade to NetBSD 9.  It is
                     51: unlikely that anyone is interested in helping, other than telling you
                     52: to upgrade to 9.
                     53: 
1.13      wiz        54: (Reports of how well NetBSD 8 works are welcome on netbsd-users, if it
1.1       gdt        55: can actually be recommended for use.)
                     56: 
                     57: ## NetBSD 9
                     58: 
                     59: There have been fixes since 9.0 RELEASE.  It is best to upgrade along
1.12      gdt        60: the netbsd-9 branch, but the release should be ok.  Most aspects work solidly.
1.1       gdt        61: 
1.12      gdt        62: \todo Explain this in terms of versions of FreeBSD OpenZFS and/or
                     63: zfsonlinux.
1.1       gdt        64: 
                     65: \todo This supports pool version 28/5000 (really true?).  Of the
                     66: feature flags found in modern OpenZFS, \todo are supported.
                     67: 
1.7       gdt        68: Generally, fixes to ZFS in current will be pulled up to 9, but new
1.5       gdt        69: features typically will not be.
                     70: 
1.1       gdt        71: ## NetBSD current
                     72: 
1.5       gdt        73: The ZFS code in current is very similar to that in 9.
                     74: 
1.9       gdt        75: There is initial support for [[ZFS root|wiki/RootOnZFS]], via booting from
1.5       gdt        76: ffs and pivoting.
1.1       gdt        77: 
1.14    ! gdt        78: One can make a ccd using a zvol as a component.  See the zvol section below.
1.1       gdt        79: 
1.13      wiz        80: ## things that aren't supported yet
1.1       gdt        81: 
1.8       gdt        82: \todo hotswap (maybe - not clear exactly what this means)
1.1       gdt        83: 
1.13      wiz        84: \todo direct boot into zfs root (via boot blocks reading zfs)
1.1       gdt        85: 
                     86: ## Architectures
                     87: 
                     88: Most people seem to be using amd64.
                     89: 
                     90: To build zfs, one puts MKZFS=yes in mk.conf.  This is default on amd64
                     91: and aarch64 on netbsd-9.  In current, it is also default on sparc64.
                     92: 
                     93: More or less, zfs can be enabled on an architecture when it is known
                     94: to build and run reliably.  (Of course, users are welcome to build it
                     95: and report.)
                     96: 
                     97: # NetBSD-specific information
                     98: 
                     99: ## rc.conf
                    100: 
                    101: The main configuration is to put zfs=YES in rc.conf, so that the rc.d
1.13      wiz       102: scripts bring up ZFS and mount ZFS file systems.
1.1       gdt       103: 
1.14    ! gdt       104: ## pool locations
        !           105: 
        !           106: One can add disks or parts of disks into pools.  Methods of specifying
        !           107: areas to be included include:
        !           108: 
        !           109:   - entire disks (e.g., /dev/rwd0d on amd64)
        !           110:   - disklabel partitions (e.g., /dev/sd0e)
        !           111:   - wedges (e.g., /dev/dk0)
        !           112: 
1.6       gdt       113: ## legacy vs ? mount points
                    114: 
                    115: \todo Explain, if this is NetBSD specific.  Explain consequences, as
                    116: this seems to have something to do with mount ordering.
                    117: 
1.1       gdt       118: ## mount order
                    119: 
1.13      wiz       120: NetBSD 9 mounts other file systems and then ZFS file systems.  This can
1.3       gdt       121: be a problem if /usr/pkgsrc is on ZFS and /usr/pkgsrc/distfiles is on
                    122: NFS.  A workaround is to use noauto and do the mounts in
                    123: /etc/rc.local.
                    124: 
                    125: NetBSD current after 20200301 mounts ZFS first. \todo Explain
                    126: consequences.
1.1       gdt       127: 
1.14    ! gdt       128: ## zvol
        !           129: 
        !           130: Within a ZFS pool, the standard approach is to have file systems, but
        !           131: one can also create a zvol, which is a block device of a certain size.
        !           132: 
        !           133: \todo The zvol will appear as /dev/???? and can be used in many
        !           134: respects like a slice.  However, the system will not read disklabels
        !           135: and gpt labels from a zvol; in this respect it is more like a disklabel
        !           136: partition or wedge than a disk drive.
        !           137: 
        !           138: \todo Explain that one can export a zvol via iscsi.
        !           139: 
        !           140: \todo Explain if one can swap on a zvol.
        !           141: 
        !           142: \todo Explain that one can use ccd to create a normal-looking disk
        !           143: from a zvol.  This allows reading a GPT label from the zvol, which is
        !           144: useful in case the zvol had been exported via iscsi and some other
        !           145: system created a label.
        !           146: 
1.1       gdt       147: ## TRIM
                    148: 
                    149: There is some notion of TRIM and zfs using it.
                    150: 
                    151: \todo Explain how this relates to NetBSD.
                    152: 
                    153: # Memory usage
                    154: 
                    155: Basically, ZFS uses lots of memory and most people run it on systems
                    156: with large amounts of memory.  NetBSD works well on systems with
                    157: comparatively small amounts of memory.  So a natural question is how
                    158: well ZFS works on one's VAX with 2M of RAM :-)
                    159: 
1.11      gdt       160: More seriously, one might ask if it is reasonable to run ZFS on a RPI3
1.1       gdt       161: with 1G of RAM, or even if it is reasonable on a system with 4G.
                    162: 
                    163: \todo Give ballpark level for minimum sane RAM, and the amount which
                    164: is cleanly enough.
                    165: 
1.10      gdt       166: For now, a good guess is that a 4G system with only 1T of disk is
                    167: probably ok, 1G is very likely not ok.
                    168: 
1.2       gdt       169: FreeBSD has some documentation about memory use.  There is a notion of
                    170: a minimum of 1G, and using 1G for 1T of storage, and more if
                    171: deduplication is enabled.  FreeBSD considers all i386 systems to be
                    172: low memory; this appears to be a clue.
1.1       gdt       173: 
1.2       gdt       174: \todo Explain if the FreeBSD sysctl list applies, or if not what we
                    175: should do instead.
                    176: 
1.7       gdt       177:   - [FreeBSD low memory documentation](https://www.freebsd.org/doc/handbook/zfs-advanced.html)
1.1       gdt       178: 
                    179: # Interoperability with other systems
                    180: 
                    181: \todo Explain pool version and feature flags relationship to FreeBSD,
                    182: Linux, OpenIndiana/Illumos/?, and ?
                    183: 
1.14    ! gdt       184: # Quick Start
        !           185: 
        !           186: See the [FreeBSD Quickstart
        !           187: Guide](https://www.freebsd.org/doc/handbook/zfs-quickstart.html); only
        !           188: the first item is NetBSD specific.
        !           189: 
        !           190:   - Put zfs=YES in rc.conf.
        !           191: 
        !           192:   - Create a pool as "zpool create pool1 /dev/dk0".
        !           193: 
        !           194:   - df and see /pool1
        !           195: 
        !           196:   - Really, read the FreeBSD docs and the 
1.1       gdt       197: 

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