File:  [NetBSD Developer Wiki] / wikisrc / zfs.mdwn
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Mon Mar 2 17:17:59 2020 UTC (22 months, 2 weeks ago) by gdt
Branches: MAIN
CVS tags: HEAD
zfs: Improve doc pointers

Inspired by a suggestion from Jason Mitchell

    1: # ZFS on NetBSD
    2: 
    3: This page attempts to do two things: provide enough orientation and
    4: pointers to standard ZFS documentation for NetBSD users who are new to
    5: ZFS, and to describe NetBSD-specific ZFS information.  It is
    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: 
   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)
   18:   - [OpenZFS admin docs index page](https://github.com/openzfs/zfs/wiki/Admin-Documentation)
   19: 
   20:   - https://en.wikipedia.org/wiki/ZFS
   21: 
   22: # Status of ZFS in NetBSD
   23: 
   24: ## Sources of ZFS code
   25: 
   26: \todo Verify/fix.
   27: 
   28: Currently, there are multiple ZFS projects and codebases:
   29: 
   30:   - ZFS as released under the CDDL (common ancestor)
   31:   - [OpenZFS](http://www.open-zfs.org/wiki/Main_Page) [github wiki](https://github.com/openzfs/zfs/wiki)
   32:   - [zfsonlinux](https://zfsonlinux.org/)
   33:   - [OpenZFS on OS X ](https://openzfsonosx.org/) [repo](https://github.com/openzfsonosx)
   34:   - proprietary ZFS in Solaris (not relevant in open source)
   35: 
   36: OpenZFS is a coordinating project to align open ZFS codebases.  There
   37: is a notion of a shared core codebase and OS-specific adaptation code.
   38: 
   39: \todo Explain clearly the relationship between OpenZFS and zfsonlinux,
   40: and also the Illumos and OSX versions.
   41: 
   42: See [FreeBSD's history](https://wiki.freebsd.org/ZFSTuningGuide).
   43: 
   44: ## NetBSD code history
   45: 
   46: \todo This section really needs help.
   47: 
   48: Before NetBSD 8, NetBSD imported ZFS code from ?
   49: 
   50: Before NetBSD 9, NetBSD imported updated ZFS code from FreeBSD.  That
   51: FreeBSD code came from ?
   52: 
   53: ## NetBSD 8 and earlier
   54: 
   55: While there is some ZFS code, it is old, and seems to have significant
   56: problems.  If one wants to use ZFS, first upgrade to NetBSD 9.  It is
   57: unlikely that anyone is interested in helping, other than telling you
   58: to upgrade to 9.
   59: 
   60: (Reports of how well NetBSD 8 works are welcome on netbsd-users, if it
   61: can actually be recommended for use.)
   62: 
   63: ## NetBSD 9
   64: 
   65: There have been fixes since 9.0 RELEASE.  It is best to upgrade along
   66: the netbsd-9 branch, but the release should be ok.  Most aspects work solidly.
   67: 
   68: \todo Explain this in terms of versions of FreeBSD OpenZFS and/or
   69: zfsonlinux.
   70: 
   71: \todo This supports pool version 28/5000 (really true?).  Of the
   72: feature flags found in modern OpenZFS, \todo are supported.
   73: 
   74: Generally, fixes to ZFS in current will be pulled up to 9, but new
   75: features typically will not be.
   76: 
   77: ## NetBSD current
   78: 
   79: The ZFS code in current is very similar to that in 9.
   80: 
   81: There is initial support for [[ZFS root|wiki/RootOnZFS]], via booting from
   82: ffs and pivoting.
   83: 
   84: One can make a ccd using a zvol as a component.  See the zvol section below.
   85: 
   86: ## Things that aren't supported yet
   87: 
   88: \todo hotswap (maybe - not clear exactly what this means)
   89: 
   90: \todo direct boot into zfs root (via boot blocks reading zfs)
   91: 
   92: ## Architectures
   93: 
   94: Most people seem to be using amd64.
   95: 
   96: To build zfs, one puts MKZFS=yes in mk.conf.  This is default on amd64
   97: and aarch64 on netbsd-9.  In current, it is also default on sparc64.
   98: 
   99: More or less, zfs can be enabled on an architecture when it is known
  100: to build and run reliably.  (Of course, users are welcome to build it
  101: and report.)
  102: 
  103: # NetBSD-specific information
  104: 
  105: ## rc.conf
  106: 
  107: The main configuration is to put zfs=YES in rc.conf, so that the rc.d
  108: scripts bring up ZFS and mount ZFS file systems.
  109: 
  110: ## pool locations
  111: 
  112: One can add disks or parts of disks into pools.  Methods of specifying
  113: areas to be included include:
  114: 
  115:   - entire disks (e.g., /dev/rwd0d on amd64)
  116:   - disklabel partitions (e.g., /dev/sd0e)
  117:   - wedges (e.g., /dev/dk0)
  118: 
  119: ## legacy vs ? mount points
  120: 
  121: \todo Explain, if this is NetBSD specific.  Explain consequences, as
  122: this seems to have something to do with mount ordering.
  123: 
  124: ## mount order
  125: 
  126: NetBSD 9 mounts other file systems and then ZFS file systems.  This can
  127: be a problem if /usr/pkgsrc is on ZFS and /usr/pkgsrc/distfiles is on
  128: NFS.  A workaround is to use noauto and do the mounts in
  129: /etc/rc.local.
  130: 
  131: NetBSD current after 20200301 mounts ZFS first. \todo Explain
  132: consequences.
  133: 
  134: ## NFS
  135: 
  136: \todo Verify if this is accurate.
  137: 
  138: zfs filesystems can be exported over NFS.  While there are zfs
  139: commands that appear to be about controlling exports, they simply
  140: print information that can be added to exports(5).
  141: 
  142: This is reported to work on 9.0 STABLE, but to cause a panic on
  143: current (20200302).
  144: 
  145: ## zvol
  146: 
  147: Within a ZFS pool, the standard approach is to have file systems, but
  148: one can also create a zvol, which is a block device of a certain size.
  149: 
  150: \todo The zvol will appear as /dev/???? and can be used in many
  151: respects like a slice.  However, the system will not read disklabels
  152: and gpt labels from a zvol; in this respect it is more like a disklabel
  153: partition or wedge than a disk drive.
  154: 
  155: \todo Explain that one can export a zvol via iscsi.
  156: 
  157: \todo Explain if one can swap on a zvol.
  158: 
  159: \todo Explain that one can use ccd to create a normal-looking disk
  160: from a zvol.  This allows reading a GPT label from the zvol, which is
  161: useful in case the zvol had been exported via iscsi and some other
  162: system created a label.
  163: 
  164: ## TRIM
  165: 
  166: There is some notion of TRIM and zfs using it.
  167: 
  168: \todo Explain how this relates to NetBSD.
  169: 
  170: # Memory usage
  171: 
  172: Basically, ZFS uses lots of memory and most people run it on systems
  173: with large amounts of memory.  NetBSD works well on systems with
  174: comparatively small amounts of memory.  So a natural question is how
  175: well ZFS works on one's VAX with 2M of RAM :-)
  176: 
  177: More seriously, one might ask if it is reasonable to run ZFS on a RPI3
  178: with 1G of RAM, or even if it is reasonable on a system with 4G.
  179: 
  180: \todo Give ballpark level for minimum sane RAM, and the amount which
  181: is cleanly enough.
  182: 
  183: For now, a good guess is that a 4G system with only 1T of disk is
  184: probably ok, and that 1G is very likely not ok.
  185: 
  186: FreeBSD has some documentation about memory use.  There is a notion of
  187: a minimum of 1G (used for ZFS), and using 1G for 1T of storage, and
  188: more if deduplication is enabled.  FreeBSD considers all i386 systems
  189: to be low memory; this appears to be a clue.
  190: 
  191: \todo Explain if the FreeBSD sysctl list applies, or if not what we
  192: should do instead.
  193: 
  194:   - [FreeBSD low memory documentation](https://www.freebsd.org/doc/handbook/zfs-advanced.html)
  195: 
  196: # Interoperability with other systems
  197: 
  198: \todo Explain pool version and feature flags relationship to FreeBSD,
  199: Linux, OpenIndiana/Illumos/?, and ?
  200: 
  201: \todo Explain how to configure a pool in terms of version/features for
  202: use with particula other systems.
  203: 
  204: # Quick Start
  205: 
  206: See the [FreeBSD Quickstart
  207: Guide](https://www.freebsd.org/doc/handbook/zfs-quickstart.html); only
  208: the first item is NetBSD specific.
  209: 
  210:   - Put zfs=YES in rc.conf.
  211: 
  212:   - Create a pool as "zpool create pool1 /dev/dk0".
  213: 
  214:   - df and see /pool1
  215: 
  216:   - Really, read the FreeBSD docs and the other linked documentation above.

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