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Mon Mar 2 00:43:05 2020 UTC (2 years, 2 months ago) by gdt
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zfs: ask for openzfs/zfsonlinux unconfusion

    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: # Status of ZFS in NetBSD
   21: 
   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: 
   36: See [FreeBSD's history](https://wiki.freebsd.org/ZFSTuningGuide)
   37: 
   38: \todo Explain the relationship between OpenZFS and zfsonlinux.
   39: 
   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 ?
   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: 
   56: (Reports of how well NetBSD 8 works are welcome on netbsd-users, if it
   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
   62: the netbsd-9 branch, but the release should be ok.  Most aspects work solidly.
   63: 
   64: \todo Explain this in terms of versions of FreeBSD OpenZFS and/or
   65: zfsonlinux.
   66: 
   67: \todo This supports pool version 28/5000 (really true?).  Of the
   68: feature flags found in modern OpenZFS, \todo are supported.
   69: 
   70: Generally, fixes to ZFS in current will be pulled up to 9, but new
   71: features typically will not be.
   72: 
   73: ## NetBSD current
   74: 
   75: The ZFS code in current is very similar to that in 9.
   76: 
   77: There is initial support for [[ZFS root|wiki/RootOnZFS]], via booting from
   78: ffs and pivoting.
   79: 
   80: One can make a ccd using a zvol as a component.  See the zvol section below.
   81: 
   82: ## things that aren't supported yet
   83: 
   84: \todo hotswap (maybe - not clear exactly what this means)
   85: 
   86: \todo direct boot into zfs root (via boot blocks reading zfs)
   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
  104: scripts bring up ZFS and mount ZFS file systems.
  105: 
  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: 
  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: 
  120: ## mount order
  121: 
  122: NetBSD 9 mounts other file systems and then ZFS file systems.  This can
  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.
  129: 
  130: ## zvol
  131: 
  132: Within a ZFS pool, the standard approach is to have file systems, but
  133: one can also create a zvol, which is a block device of a certain size.
  134: 
  135: \todo The zvol will appear as /dev/???? and can be used in many
  136: respects like a slice.  However, the system will not read disklabels
  137: and gpt labels from a zvol; in this respect it is more like a disklabel
  138: partition or wedge than a disk drive.
  139: 
  140: \todo Explain that one can export a zvol via iscsi.
  141: 
  142: \todo Explain if one can swap on a zvol.
  143: 
  144: \todo Explain that one can use ccd to create a normal-looking disk
  145: from a zvol.  This allows reading a GPT label from the zvol, which is
  146: useful in case the zvol had been exported via iscsi and some other
  147: system created a label.
  148: 
  149: ## TRIM
  150: 
  151: There is some notion of TRIM and zfs using it.
  152: 
  153: \todo Explain how this relates to NetBSD.
  154: 
  155: # Memory usage
  156: 
  157: Basically, ZFS uses lots of memory and most people run it on systems
  158: with large amounts of memory.  NetBSD works well on systems with
  159: comparatively small amounts of memory.  So a natural question is how
  160: well ZFS works on one's VAX with 2M of RAM :-)
  161: 
  162: More seriously, one might ask if it is reasonable to run ZFS on a RPI3
  163: with 1G of RAM, or even if it is reasonable on a system with 4G.
  164: 
  165: \todo Give ballpark level for minimum sane RAM, and the amount which
  166: is cleanly enough.
  167: 
  168: For now, a good guess is that a 4G system with only 1T of disk is
  169: probably ok, 1G is very likely not ok.
  170: 
  171: FreeBSD has some documentation about memory use.  There is a notion of
  172: a minimum of 1G, and using 1G for 1T of storage, and more if
  173: deduplication is enabled.  FreeBSD considers all i386 systems to be
  174: low memory; this appears to be a clue.
  175: 
  176: \todo Explain if the FreeBSD sysctl list applies, or if not what we
  177: should do instead.
  178: 
  179:   - [FreeBSD low memory documentation](https://www.freebsd.org/doc/handbook/zfs-advanced.html)
  180: 
  181: # Interoperability with other systems
  182: 
  183: \todo Explain pool version and feature flags relationship to FreeBSD,
  184: Linux, OpenIndiana/Illumos/?, and ?
  185: 
  186: # Quick Start
  187: 
  188: See the [FreeBSD Quickstart
  189: Guide](https://www.freebsd.org/doc/handbook/zfs-quickstart.html); only
  190: the first item is NetBSD specific.
  191: 
  192:   - Put zfs=YES in rc.conf.
  193: 
  194:   - Create a pool as "zpool create pool1 /dev/dk0".
  195: 
  196:   - df and see /pool1
  197: 
  198:   - Really, read the FreeBSD docs and the 
  199: 

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