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zfs: point to RootOnZFS

    1: # ZFS on NetBSD
    2: 
    3: This page attempts to do two things: provide enough orientatino and
    4: pointers to standard ZFS documentation for NetBSD users who are new to
    5: ZFS, and to 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: 
   19: # Status of ZFS in NetBSD
   20: 
   21: NetBSD has imported OpenZFS.  \todo versions, links
   22: 
   23: ## NetBSD 8 and earlier
   24: 
   25: While there is some ZFS code, it is old, and seems to have significant
   26: problems.  If one wants to use ZFS, first upgrade to NetBSD 9.  It is
   27: unlikely that anyone is interested in helping, other than telling you
   28: to upgrade to 9.
   29: 
   30: (Reports of how well NetBDS 8 works are welcome on netbsd-users, if it
   31: can actually be recommended for use.)
   32: 
   33: ## NetBSD 9
   34: 
   35: There have been fixes since 9.0 RELEASE.  It is best to upgrade along
   36: the netbsd-9 branch, but the release should be ok.
   37: 
   38: \todo This is OpenZFS as of X.   Most aspects work solidly.
   39: 
   40: \todo This supports pool version 28/5000 (really true?).  Of the
   41: feature flags found in modern OpenZFS, \todo are supported.
   42: 
   43: Generlly, fixes to ZFS in current will be pulled up to 9, but new
   44: features typically will not be.
   45: 
   46: ## NetBSD current
   47: 
   48: The ZFS code in current is very similar to that in 9.
   49: 
   50: There is initial support for [[RootOnZFS|ZFS root]], via booting from
   51: ffs and pivoting.
   52: 
   53: One can make a ccd using a zvol as a component.  This allows reading a
   54: GPT label from the zvol, which is useful in case the zvol had been
   55: exported via iscsi and some other system created a label.
   56: 
   57: ## things that aren't suported yet
   58: 
   59: \todo (?) hotswap
   60: 
   61: \todo (?) direct boot into zfs root
   62: 
   63: ## Architectures
   64: 
   65: Most people seem to be using amd64.
   66: 
   67: To build zfs, one puts MKZFS=yes in mk.conf.  This is default on amd64
   68: and aarch64 on netbsd-9.  In current, it is also default on sparc64.
   69: 
   70: More or less, zfs can be enabled on an architecture when it is known
   71: to build and run reliably.  (Of course, users are welcome to build it
   72: and report.)
   73: 
   74: # NetBSD-specific information
   75: 
   76: ## rc.conf
   77: 
   78: The main configuration is to put zfs=YES in rc.conf, so that the rc.d
   79: scripts bring up ZFS and mount ZFS filesystems.
   80: 
   81: ## mount order
   82: 
   83: NetBSD 9 mounts other filesystems and then ZFS filesystems.  This can
   84: be a problem if /usr/pkgsrc is on ZFS and /usr/pkgsrc/distfiles is on
   85: NFS.  A workaround is to use noauto and do the mounts in
   86: /etc/rc.local.
   87: 
   88: NetBSD current after 20200301 mounts ZFS first. \todo Explain
   89: consequences.
   90: 
   91: ## TRIM
   92: 
   93: There is some notion of TRIM and zfs using it.
   94: 
   95: \todo Explain how this relates to NetBSD.
   96: 
   97: # Memory usage
   98: 
   99: Basically, ZFS uses lots of memory and most people run it on systems
  100: with large amounts of memory.  NetBSD works well on systems with
  101: comparatively small amounts of memory.  So a natural question is how
  102: well ZFS works on one's VAX with 2M of RAM :-)
  103: 
  104: More seriously, one might ask if is reasonable to run ZFS on a RPI3
  105: with 1G of RAM, or even if it is reasonable on a system with 4G.
  106: 
  107: \todo Give ballpark level for minimum sane RAM, and the amount which
  108: is cleanly enough.
  109: 
  110: FreeBSD has some documentation about memory use.  There is a notion of
  111: a minimum of 1G, and using 1G for 1T of storage, and more if
  112: deduplication is enabled.  FreeBSD considers all i386 systems to be
  113: low memory; this appears to be a clue.
  114: 
  115: \todo Explain if the FreeBSD sysctl list applies, or if not what we
  116: should do instead.
  117: 
  118: [FreeBSD low memory documentation](https://www.freebsd.org/doc/handbook/zfs-advanced.html)
  119: 
  120: # Interoperability with other systems
  121: 
  122: \todo Explain pool version and feature flags relationship to FreeBSD,
  123: Linux, OpenIndiana/Illumos/?, and ?
  124: 
  125: 

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