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Top Forums UNIX for Beginners Questions & Answers Should I use a CoW filesystem on my PC if I only wanted snapshot capabilities ? Post 303044797 by stomp on Wednesday 4th of March 2020 05:42:58 AM
Old 03-04-2020
Another comment:

A con against zfs is the inability to remove VDEVs. A VDEV is a subpart of a volume.

Example:

Say you have a data volume consisting of a single disk(=vdev, 1 TB). You decide to replace your vdev of a single disk with a raid-1 vdev(1 TB), since you want add redundancy to be safe in case of a disk crash. That's possible. Over the years, you add another 2 vdevs(2x2TB,2x4TB) with raid-1 arrays. So you then have 3 vdevs making up your volume consisting of 2 disks each with an overall capacity of 7 TB.

You now decide you want to increase your storage again and simultaneously reorganize your 3 x raid1(6 disks=>7 TB usable) to 1 x raidz2(5x6 TB =>18 TB usable) to be able to cope with more simulateous disk crashes(2 disk crashes without data loss here) and at the same time reduce the number of active disks(6->5).

With zfs this is only possible by reformatting, since device removal is not fully supported by now. So you have to copy all the data, which must be done offline. ZFS top level device removal is in development at the moment, but i expect some years to pass until even raidz vdevs can be removed.

With LVM you can just add the new underlying disks and remove the old disks. No problem. All is possible to be done online. Btrfs can do that to and is even flexible to do more advanced migrations.

And Here are some experience reports about btrfs and zfs from users:

ZFS Vs BTRFS : linux

Some not to long gone data loss stories about btrfs are also there. I assume the cause may be lacking knowledge about file system operation. But of course that's only a suspicion.

Last edited by stomp; 03-04-2020 at 06:52 AM..
 

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ZFS-FUSE(8)							  [FIXME: manual]						       ZFS-FUSE(8)

NAME
zfs-fuse - ZFS filesystem daemon SYNOPSIS
zfs-fuse [--pidfile filename] [--no-daemon] [--no-kstat-mount] [--disable-block-cache] [--disable-page-cache] [--fuse-attr-timeout SECONDS] [--fuse-entry-timeout SECONDS] [--log-uberblocks] [--max-arc-size MB] [--fuse-mount-options OPT,OPT,OPT...] [--min-uberblock-txg MIN] [--stack-size=size] [--enable-xattr] [--help] DESCRIPTION
This manual page documents briefly the zfs-fuse command. zfs-fuse is a daemon which provides support for the ZFS filesystem, via fuse. Ordinarily this daemon will be invoked from system boot scripts. OPTIONS
This program follows the usual GNU command line syntax, with long options starting with two dashes (`-'). A summary of options is included below. For a complete description, see the Info files. -h --help Show summary of options. -p filename --pidfile filename Write the daemon's PID to filename after daemonizing. Ignored if --no-daemon is passed. filename should be a fully-qualified path. -n --no-daemon Stay in foreground, don't daemonize. --no-kstat-mount Do not mount kstats in /zfs-kstat --disable-block-cache Enable direct I/O for disk operations. Completely disables caching reads and writes in the kernel block cache. Breaks mmap() in ZFS datasets too. --disable-page-cache Disable the page cache for files residing within ZFS filesystems. Not recommended as it slows down I/O operations considerably. -a SECONDS --fuse-attr-timeout SECONDS Sets timeout for caching FUSE attributes in kernel. Defaults to 0.0. Higher values give a 40% performance boost. -e SECONDS --fuse-entry-timeout SECONDS Sets timeout for caching FUSE entries in kernel. Defaults to 0.0. Higher values give a 10000% performance boost but cause file permission checking security issues. --log-uberblocks Logs uberblocks of any mounted filesystem to syslog -m MB --max-arc-size MB Forces the maximum ARC size (in megabytes). Range: 16 to 16384. -o OPT... --fuse-mount-options OPT,OPT,OPT... Sets FUSE mount options for all filesystems. Format: comma-separated string of characters. -u MIN --min-uberblock-txg MIN Skips uberblocks with a TXG < MIN when mounting any fs -v MB --vdev-cache-size MB adjust the size of the vdev cache. Default : 10 --zfs-prefetch-disable Disable the high level prefetch cache in zfs. This thing can eat up to 150 Mb of ram, maybe more --stack-size=size Limit the stack size of threads (in kb). default : no limit (8 Mb for linux) -x --enable-xattr Enable support for extended attributes. Not generally recommended because it currently has a significant performance penalty for many small IOPS -h --help Show this usage summary. REMARKS ON PRECEDENCE
Note that the parameters passed on the command line take precedence over those supplied through /etc/zfs/zfsrc. BUGS
/CAVEATS The path to the configuration file (/etc/zfs/zfsrc) cannot at this time be configured. Most existing packages suggest settings can be set at the top of their init script. These get frequently overridden by a (distribution specific) /etc/default/zfs-fuse file, if it exists. Be sure to look at these places if you want your changes to options to take effect. The /etc/zfs/zfsrc is going to be the recommended approach in the future. So, packagers, please refrain from passing commandline parameters within the initscript (except for --pid-file). SEE ALSO
zfs (8), zpool (8), zdb(8), zstreamdump(8), /etc/zfs/zfsrc AUTHOR
This manual page was written by Bryan Donlan bdonlan@gmail.com for the Debian(TM) system (but may be used by others). Permission is granted to copy, distribute and/or modify this document under the terms of the GNU General Public License, Version 2 any later version published by the Free Software Foundation, or the Common Development and Distribution License. Revised by Seth Heeren zfs-fuse@sehe.nl On Debian systems, the complete text of the GNU General Public License can be found in /usr/share/common-licenses/GPL. The text of the Common Development and Distribution Licence may be found at /usr/share/doc/zfs-fuse/copyright COPYRIGHT
Copyright (C) 2010 Bryan Donlan [FIXME: source] 2010-06-09 ZFS-FUSE(8)
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