Return to zfs.mdwn CVS log

Up to [NetBSD Developer Wiki] / wikisrc

zfs: improve code heritage section

Thanks to prlw1@ for hints, but mistakes are still my fault.

    1: # ZFS on NetBSD
    2: 
    3: This page attempts to do two things: provide enough orientation and
    4: pointers to dstandard 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: 
   19: # Status of ZFS in NetBSD
   20: 
   21: ## Sources
   22: 
   23: \todo Verify/fix.
   24: 
   25: Currently, there are multiple ZFS projects/codebases:
   26: 
   27:   - ZFS as released under the CDDL (common ancestor)
   28:   - [OpenZFS](http://www.open-zfs.org/wiki/Main_Page)
   29:   - [zfsonlinux](https://zfsonlinux.org/)
   30:   - proprietary ZFS in Solaris (not relevant in open source)
   31: 
   32: OpenZFS is a coordinating project to align open ZFS codebases.  There
   33: is a notion of a shared core codebase and OS-specific adaptation code.
   34: 
   35: ## NetBSD code history
   36: 
   37: \todo This section really needs help.
   38: 
   39: Before NetBSD 8, NetBSD imported ZFS code from ?
   40: 
   41: Before NetBSD 9, NetBSD imported updated ZFS code from FreeBSD.  That
   42: FreeBSD code came from ?
   43: 
   44: ## NetBSD 8 and earlier
   45: 
   46: While there is some ZFS code, it is old, and seems to have significant
   47: problems.  If one wants to use ZFS, first upgrade to NetBSD 9.  It is
   48: unlikely that anyone is interested in helping, other than telling you
   49: to upgrade to 9.
   50: 
   51: (Reports of how well NetBDS 8 works are welcome on netbsd-users, if it
   52: can actually be recommended for use.)
   53: 
   54: ## NetBSD 9
   55: 
   56: There have been fixes since 9.0 RELEASE.  It is best to upgrade along
   57: the netbsd-9 branch, but the release should be ok.  Most aspects work solidly.
   58: 
   59: \todo Explain this in terms of versions of FreeBSD OpenZFS and/or
   60: zfsonlinux.
   61: 
   62: \todo This supports pool version 28/5000 (really true?).  Of the
   63: feature flags found in modern OpenZFS, \todo are supported.
   64: 
   65: Generally, fixes to ZFS in current will be pulled up to 9, but new
   66: features typically will not be.
   67: 
   68: ## NetBSD current
   69: 
   70: The ZFS code in current is very similar to that in 9.
   71: 
   72: There is initial support for [[ZFS root|wiki/RootOnZFS]], via booting from
   73: ffs and pivoting.
   74: 
   75: One can make a ccd using a zvol as a component.  This allows reading a
   76: GPT label from the zvol, which is useful in case the zvol had been
   77: exported via iscsi and some other system created a label.
   78: 
   79: ## things that aren't suported yet
   80: 
   81: \todo hotswap (maybe - not clear exactly what this means)
   82: 
   83: \todo direct boot into zfs root (via bootblocks reading zfs)
   84: 
   85: ## Architectures
   86: 
   87: Most people seem to be using amd64.
   88: 
   89: To build zfs, one puts MKZFS=yes in mk.conf.  This is default on amd64
   90: and aarch64 on netbsd-9.  In current, it is also default on sparc64.
   91: 
   92: More or less, zfs can be enabled on an architecture when it is known
   93: to build and run reliably.  (Of course, users are welcome to build it
   94: and report.)
   95: 
   96: # NetBSD-specific information
   97: 
   98: ## rc.conf
   99: 
  100: The main configuration is to put zfs=YES in rc.conf, so that the rc.d
  101: scripts bring up ZFS and mount ZFS filesystems.
  102: 
  103: ## legacy vs ? mount points
  104: 
  105: \todo Explain, if this is NetBSD specific.  Explain consequences, as
  106: this seems to have something to do with mount ordering.
  107: 
  108: ## mount order
  109: 
  110: NetBSD 9 mounts other filesystems and then ZFS filesystems.  This can
  111: be a problem if /usr/pkgsrc is on ZFS and /usr/pkgsrc/distfiles is on
  112: NFS.  A workaround is to use noauto and do the mounts in
  113: /etc/rc.local.
  114: 
  115: NetBSD current after 20200301 mounts ZFS first. \todo Explain
  116: consequences.
  117: 
  118: ## TRIM
  119: 
  120: There is some notion of TRIM and zfs using it.
  121: 
  122: \todo Explain how this relates to NetBSD.
  123: 
  124: # Memory usage
  125: 
  126: Basically, ZFS uses lots of memory and most people run it on systems
  127: with large amounts of memory.  NetBSD works well on systems with
  128: comparatively small amounts of memory.  So a natural question is how
  129: well ZFS works on one's VAX with 2M of RAM :-)
  130: 
  131: More seriously, one might ask if it is reasonable to run ZFS on a RPI3
  132: with 1G of RAM, or even if it is reasonable on a system with 4G.
  133: 
  134: \todo Give ballpark level for minimum sane RAM, and the amount which
  135: is cleanly enough.
  136: 
  137: For now, a good guess is that a 4G system with only 1T of disk is
  138: probably ok, 1G is very likely not ok.
  139: 
  140: FreeBSD has some documentation about memory use.  There is a notion of
  141: a minimum of 1G, and using 1G for 1T of storage, and more if
  142: deduplication is enabled.  FreeBSD considers all i386 systems to be
  143: low memory; this appears to be a clue.
  144: 
  145: \todo Explain if the FreeBSD sysctl list applies, or if not what we
  146: should do instead.
  147: 
  148:   - [FreeBSD low memory documentation](https://www.freebsd.org/doc/handbook/zfs-advanced.html)
  149: 
  150: # Interoperability with other systems
  151: 
  152: \todo Explain pool version and feature flags relationship to FreeBSD,
  153: Linux, OpenIndiana/Illumos/?, and ?
  154: 
  155: