Annotation of wikisrc/zfs.mdwn, revision 1.31
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
1.28 gdt 9: explanation, and some have question marks
1.1 gdt 10:
11: # Documentation Pointers
12:
13: See the man pages for zfs(8) and zpool(8).
14:
1.27 gdt 15: - [OpenZFS Documentation](https://openzfs.github.io/openzfs-docs/)
16: - [OpenZFS admin docs index page](https://github.com/openzfs/zfs/wiki/Admin-Documentation)
17: - [FreeBSD Handbook ZFS Chapter](https://www.freebsd.org/doc/handbook/zfs.html)
1.4 gdt 18: - [Oracle ZFS Administration Manual](https://docs.oracle.com/cd/E26505_01/html/E37384/index.html)
1.24 gdt 19: - [Wikipedia](https://en.wikipedia.org/wiki/ZFS)
1.21 gdt 20:
1.1 gdt 21: # Status of ZFS in NetBSD
22:
1.27 gdt 23: ## NetBSD 8
1.23 gdt 24:
1.27 gdt 25: NetBSD 8 has an old version of ZFS, and it is not recommended for use
26: at all. There is no evidence that anyone is interested in helping
27: with ZFS on 8. Those wishing to use ZFS on NetBSD 8 should therefore
28: update to NetBSD 9.
1.1 gdt 29:
30: ## NetBSD 9
31:
1.27 gdt 32: NetBSD-9 has ZFS that is considered to work well. There have been
33: fixes since 9.0_RELEASE. As always, people running NetBSD 9 are
34: likely best served by the most recent version of the netbsd-9 stable
35: branch. As of 2021-02, ZFS in the NetBSD 9.1 release is very close to
36: netbsd-9.
1.1 gdt 37:
1.27 gdt 38: ## NetBSD-current
1.1 gdt 39:
1.27 gdt 40: NetBSD-current (as of 2021-02) has similar ZFS code to 9.
1.5 gdt 41:
1.9 gdt 42: There is initial support for [[ZFS root|wiki/RootOnZFS]], via booting from
1.5 gdt 43: ffs and pivoting.
1.1 gdt 44:
1.27 gdt 45: ## NetBSD/xen special issues
1.1 gdt 46:
1.27 gdt 47: In NetBSD-9, MAXPHYS is 64KB in most places, but because of xbd(4) it
48: is set to 32KB for XEN kernels. Thus the standard zfs kernel modules
49: do not work under xen. In NetBSD-current, xbd(4) supports 64 KB
50: MAXPHYS and this is no longer an issue.
1.1 gdt 51:
1.27 gdt 52: Xen and zfs on current are reported to work well together, as of 2021-02.
1.1 gdt 53:
54: ## Architectures
55:
56: Most people seem to be using amd64.
57:
58: To build zfs, one puts MKZFS=yes in mk.conf. This is default on amd64
59: and aarch64 on netbsd-9. In current, it is also default on sparc64.
60:
61: More or less, zfs can be enabled on an architecture when it is known
62: to build and run reliably. (Of course, users are welcome to build it
63: and report.)
64:
1.27 gdt 65: # Quick Start
66:
67: See the [FreeBSD Quickstart
68: Guide](https://www.freebsd.org/doc/handbook/zfs-quickstart.html); only
69: the first item is NetBSD specific.
70:
71: - Put zfs=YES in rc.conf.
72:
73: - Create a pool as "zpool create pool1 /dev/dk0".
74:
75: - df and see /pool1
76:
77: - Create a filesystem mounted on /n0 as "zfs create -o
78: mountpoint=/n0 pool1/n0".
79:
80: - Go back and read the documentation and start over.
81:
1.1 gdt 82: # NetBSD-specific information
83:
84: ## rc.conf
85:
86: The main configuration is to put zfs=YES in rc.conf, so that the rc.d
1.13 wiz 87: scripts bring up ZFS and mount ZFS file systems.
1.1 gdt 88:
1.14 gdt 89: ## pool locations
90:
91: One can add disks or parts of disks into pools. Methods of specifying
92: areas to be included include:
93:
1.29 gdt 94: - entire disks (e.g., /dev/wd0d on amd64, or /dev/wd0 which has the same major/minor)
1.14 gdt 95: - disklabel partitions (e.g., /dev/sd0e)
96: - wedges (e.g., /dev/dk0)
97:
1.1 gdt 98: ## mount order
99:
1.13 wiz 100: NetBSD 9 mounts other file systems and then ZFS file systems. This can
1.3 gdt 101: be a problem if /usr/pkgsrc is on ZFS and /usr/pkgsrc/distfiles is on
102: NFS. A workaround is to use noauto and do the mounts in
103: /etc/rc.local.
104:
1.27 gdt 105: NetBSD current after 20200301 mounts ZFS first. The same issues and
106: workarounds apply in different circumstances.
1.1 gdt 107:
1.19 gdt 108: ## NFS
109:
1.31 ! gdt 110: zfs filesystems can be exported via NFS, simply by placing them in
! 111: /etc/exports like any other filesystem.
1.27 gdt 112:
1.31 ! gdt 113: The "zfs share" command adds a line for each filesystem with the
! 114: sharenfs property set to /etc/zfs/exports, and "zfs unshare" removes
! 115: it. \todo Explain if /etc/zfs/exports is used and whether this makes
! 116: any sense on NetBSD.
! 117:
! 118: On current as of 20210214, a remote mkdir of a filesystem mounted via
! 119: -maproot=0:10 causes a kernel NULL pointer dereference. This is now
! 120: understood and expected to be fixed very soon. See
! 121: [misc/55042](http://gnats.netbsd.org/55042).
1.20 gdt 122:
1.14 gdt 123: ## zvol
124:
125: Within a ZFS pool, the standard approach is to have file systems, but
126: one can also create a zvol, which is a block device of a certain size.
127:
128: \todo The zvol will appear as /dev/???? and can be used in many
129: respects like a slice. However, the system will not read disklabels
130: and gpt labels from a zvol; in this respect it is more like a disklabel
131: partition or wedge than a disk drive.
132:
133: \todo Explain that one can export a zvol via iscsi.
134:
135: \todo Explain if one can swap on a zvol.
136:
137: \todo Explain that one can use ccd to create a normal-looking disk
138: from a zvol. This allows reading a GPT label from the zvol, which is
139: useful in case the zvol had been exported via iscsi and some other
140: system created a label.
141:
1.1 gdt 142: # Memory usage
143:
144: Basically, ZFS uses lots of memory and most people run it on systems
145: with large amounts of memory. NetBSD works well on systems with
146: comparatively small amounts of memory. So a natural question is how
1.27 gdt 147: well ZFS works on one's VAX with 2M of RAM :-) More seriously, one
148: might ask if it is reasonable to run ZFS on a RPI3 with 1G of RAM, or
149: if it is reasonable on a system with 4G.
150:
151: The prevailing wisdom is more or less that ZFS consumes 1G plus 1G per
152: 1T of disk. 32-bit architectures are viewed as too small to run ZFS.
153:
154: Besides RAM, zfs requires that architecture kernel stack size is at
155: least 12KB or more -- some operations cause stack overflow with 8KB
156: kernel stack. On NetBSD, the architectures with 16KB kernel stack are
157: amd64, sparc64, powerpc, and experimental ia64, hppa. mac68k and sh3
158: have 12KB kernel stack. All others use only 8KB stack, which is not
159: enough to run zfs.
160:
161: NetBSD has many statistics provided via sysctl; see "sysctl
162: kstat.zfs".
163:
164: FreeBSD has tunables that NetBSD does not seem to have, described in
165: [FreeBSD Handbook ZFS Advanced
166: section](https://docs.freebsd.org/en/books/handbook/zfs/#zfs-advanced).
1.1 gdt 167:
1.27 gdt 168: # Interoperability with other systems
1.1 gdt 169:
1.27 gdt 170: Modern ZFS uses pool version 5000 and feature flags.
1.1 gdt 171:
1.27 gdt 172: It is in general possible to export a pool and them import the pool on
173: some other system, as long as the other system supports all the used
174: features.
1.10 gdt 175:
1.27 gdt 176: \todo Explain how to do this and what is known to work.
1.26 wiki 177:
1.27 gdt 178: \todo Explain feature flags relationship to FreeBSD, Linux, iIllumos,
179: macOS.
1.1 gdt 180:
1.27 gdt 181: # Sources of ZFS code
1.2 gdt 182:
1.27 gdt 183: Currently, there are multiple ZFS projects and codebases:
1.1 gdt 184:
1.27 gdt 185: - [OpenZFS](http://www.open-zfs.org/wiki/Main_Page)
1.30 wiz 186: - [openzfs repository](https://github.com/openzfs/zfs)
1.27 gdt 187: - [zfsonlinux](https://zfsonlinux.org/)
188: - [OpenZFS on OS X ](https://openzfsonosx.org/) [repo](https://github.com/openzfsonosx)
189: - proprietary ZFS in Solaris (not relevant in open source)
190: - ZFS as released under the CDDL (common ancestor, now of historical interest)
1.1 gdt 191:
1.27 gdt 192: OpenZFS is a coordinating project to align open ZFS codebases. There
193: is a notion of a shared core codebase and OS-specific adaptation code.
1.1 gdt 194:
1.27 gdt 195: - [zfsonlinux relationship to OpenZFS](https://github.com/openzfs/zfs/wiki/OpenZFS-Patches)
1.28 gdt 196: - FreeBSD more or less imports code from openzfs and pushes back fixes. \todo Verify this.
197: - NetBSD has imported code from FreeBSD.
198: - The status of ZFS on macOS is unclear (2021-02).
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