<html dir="ltr"><head></head><body style="text-align:left; direction:ltr;"><div>You don't seem to need to mount a subvolume but everyone seems to do it, because if you have a problem, you can unmount it and mount the latest snapshot.</div><div><br></div><div>According to one website, Suse has subvolumes for /, /backups. /home, /opt, /root, /srv, /usr/local, /tmp, and /var. Some are so you don't overwrite data if you do a rollback. /tmp and /var hold temporary files, so there's no need to snapshot them. This is too complicated for some people, so they only have subvolumes for / and /home.</div><div><br></div><div>I don't know if you need to make a subvoolume for /tmp if you are using tmpfs or ZRAM. I'd never heard of ZRAM but NextcloudPi uses it for /tmp.</div><div><br></div><div>Suse has a utility called snapper that make it easy to manage subvolumes, but I haven't looked at it yet.</div><div> </div><div>Btrfs apparently can handle swap files now. You want to truncate it every time you boot to get rid of old data, and then use fallocate to expand it back to the size you want before running mkswap and swapon on it. You also need to run "sudo chattr +C swapfile" to disable copy on write. Maybe there's a systemd unit file for this.</div><div><br></div><div><br></div><div>On Sun, 2019-03-31 at 17:00 -0600, Chris Fedde wrote:</div><blockquote type="cite" style="margin:0 0 0 .8ex; border-left:2px #729fcf solid;padding-left:1ex"><div dir="ltr"><div>The ZFS approach is typically to have way more mount points than we might have with a classic file system. Each users home directory for example might be a mount point. Any of your data, logging and other write heavy directories might each have a different mount point. Using this scheme then you can apply whatever filesystem attributes you want to a "directory" by converting it to a mount point. There are workflows that make this kind of migration pretty easy. Eventually it begins to seem "normal" to work this way. Of course it's not too hard to normalize anything.</div><div><br></div><div>ZFS itself remembers the configuration, so management of all these mount points is not as burdensome is it might seem at first. <br></div></div><br><div class="gmail_quote"><div dir="ltr" class="gmail_attr">On Sun, Mar 31, 2019 at 1:26 PM dennisjperkins <<a href="mailto:dennisjperkins@comcast.net">dennisjperkins@comcast.net</a>> wrote:<br></div><blockquote type="cite" style="margin:0 0 0 .8ex; border-left:2px #729fcf solid;padding-left:1ex"><div><div><font face="sans-serif">Btrfs seems more flexible for snapshots, but that can also mean more complicated if you are not careful. You can only take snapshots of a subvolume. You might not want a snapshot if everything in /, like /home or /temp, but if you make these subvolumes, a snapshot of / will not include them because Btrfs won't include embedded subvolumes in a snapshot. </font></div><div><br></div><div><br></div><div><br></div><div id="gmail-m_-4265875888698312093composer_signature"><div style="font-size:85%;color:rgb(87,87,87)" dir="auto">Sent from my Galaxy Tab® S2</div></div><div><br></div><div style="font-size:100%;color:rgb(0,0,0)"><div>-------- Original message --------</div><div>From: Sean LeBlanc <<a href="mailto:seanleblanc@comcast.net" target="_blank">seanleblanc@comcast.net</a>> </div><div>Date: 3/31/19 11:39 AM (GMT-07:00) </div><div>To: <a href="mailto:clue@cluedenver.org" target="_blank">clue@cluedenver.org</a> </div><div>Subject: Re: [clue] btrfs vs ZFS question </div><div><br></div></div>
<div class="gmail-m_-4265875888698312093moz-cite-prefix">I think he might have meant me, but you
saw it first and probably had more info anyway, so it works out.
:)</div>
<div class="gmail-m_-4265875888698312093moz-cite-prefix"><br>
</div>
<div class="gmail-m_-4265875888698312093moz-cite-prefix">My experience with ZFS has - so far -
been somewhat at arms' length. I've been using it via FreeNAS and
about the only thing I've done of any consequence is replace each
drive, let it resilver, then move on to the other, until the
entire set has been expanded. *knocks on wood* I kind of want this
sort of storage to be boring, but reliable.<br>
</div>
<div class="gmail-m_-4265875888698312093moz-cite-prefix"><br>
</div>
<div class="gmail-m_-4265875888698312093moz-cite-prefix">From what I can tell - and I only
looked a little bit about 5 years ago or so - btrfs has more
promise as far as features, and is not a pain to get to work under
Linux (as opposed to things like ZoL), but in the opinion of some
at the time, btrfs seemed a bit more, um, sketchy. ZFS had the
advantage of a lot of research early on by Sun/Oracle, and then
the OpenZFS fork made it for the world and move beyond just
Solaris. It's a shame that it seems mostly still confined to
FreeBSD. I don't mind FreeBSD, and actually like a few things
about it, but I realize that easy Linux interop is going to make
adoption much higher.</div>
<div class="gmail-m_-4265875888698312093moz-cite-prefix"><br>
</div>
<div class="gmail-m_-4265875888698312093moz-cite-prefix">Seems that btrfs is much more mature
now and probably has more features than OpenZFS? Since Dennis'
links prompted me to do more reading on it again, it does seem the
CoW feature per file is an interesting one for sure, if I
understand it correctly.</div>
<div class="gmail-m_-4265875888698312093moz-cite-prefix"><br>
</div>
<div class="gmail-m_-4265875888698312093moz-cite-prefix">Also based on comments or in articles
themselves, I still may take a Pi and use that as a way of
shipping deltas from my ZFS pools to a Pi running FreeBSD. Someone
had mentioned they were doing incremental backups of very large
dataset (53Tb?) to a Pi in this way. Seems a good way to have some
(extra) assurances of your data - at least if you are already
using ZFS.<br>
</div>
<div class="gmail-m_-4265875888698312093moz-cite-prefix"><br>
</div>
<div class="gmail-m_-4265875888698312093moz-cite-prefix">On 3/27/19 9:33 PM, Shawn Perry wrote:<br>
</div>
<blockquote type="cite" style="margin:0 0 0 .8ex; border-left:2px #729fcf solid;padding-left:1ex">
<div class="gmail-m_-4265875888698312093WordSection1">
<p class="MsoNormal">I’m assuming you mean me, so I’ll answer.</p>
<p class="MsoNormal"><u></u> <u></u></p>
<ol style="margin-top:0in" start="1" type="1">
<li class="gmail-m_-4265875888698312093MsoListParagraph" style="margin-left:0in">You can add.
You should add in the same pattern that already exists to
maintain performance and redundancy. If you have a 4 disk
raid 5, you should add 4 more disks in a raid 5 config.</li>
<ol style="margin-top:0in" start="1" type="a">
<li class="gmail-m_-4265875888698312093MsoListParagraph" style="margin-left:0in">You cannot
remove yet. 0.8x will allow removing, but only to cover
accidental adds.</li>
</ol>
<li class="gmail-m_-4265875888698312093MsoListParagraph" style="margin-left:0in">You can
resize up. If you replace a disk with a larger one, you can
expand the space. If you add more disks, you can use the
extra space.</li>
<ol style="margin-top:0in" start="1" type="a">
<li class="gmail-m_-4265875888698312093MsoListParagraph" style="margin-left:0in">You cannot
shrink or remove.</li>
</ol>
<li class="gmail-m_-4265875888698312093MsoListParagraph" style="margin-left:0in">The data
does not need balancing unless you add disks. To rebalance,
you would need to re-copy the data. You can use send/recv to
do that. You’d need to stop things to do this. The actual
stoppage will be only the amount of time it takes you to
type “zfs rename <source> <destination>” twice.
Once to move the old out of the way, once to move the new
back to the original location.</li>
<li class="gmail-m_-4265875888698312093MsoListParagraph" style="margin-left:0in">Sorta. You
can split mirrors in a raid 1 or raid 10 config to drop down
to a single disk or raid 0, respectively. You cannot reshape
like md or btrfs.</li>
</ol>
<p class="MsoNormal"><u></u> <u></u></p>
<div style="border-color:rgb(225,225,225) currentcolor currentcolor;border-style:solid none none;border-width:1pt medium medium;padding:3pt 0in 0in">
<p class="MsoNormal" style="border:medium none;padding:0in"><b>From:
</b><a href="mailto:dennisjperkins@comcast.net" target="_blank">Dennis J Perkins</a><br>
<b>Sent: </b>Wednesday, March 27, 2019 9:23 PM<br>
<b>To: </b><a href="mailto:clue@cluedenver.org" target="_blank">CLUE's mailing list</a><br>
<b>Subject: </b>[clue] btrfs vs ZFS question</p>
</div>
<p class="MsoNormal"><u></u> <u></u></p>
<p class="MsoNormal">Sean, does ZFS let you do these things?</p>
<p class="MsoNormal"><u></u> <u></u></p>
<p class="MsoNormal">Btrfs lets you do the following without
stopping anything:</p>
<p class="MsoNormal"><u></u> <u></u></p>
<p class="MsoNormal">1. Add or remove partitions. If you remove
a partition, make sure the</p>
<p class="MsoNormal">remaining drives have enough capacity.</p>
<p class="MsoNormal">2. Resize a btrfs system.</p>
<p class="MsoNormal">3. Balance the data.</p>
<p class="MsoNormal">4. Switch between single disk, RAID 0, RAID
1, or RAID 10 configs.</p>
<p class="MsoNormal"><u></u> <u></u></p>
<p class="MsoNormal">Shuffling data around as a result of any of
these operatins is done in</p>
<p class="MsoNormal">the background and might take hours.</p>
<p class="MsoNormal"><u></u> <u></u></p>
<p class="MsoNormal">_______________________________________________</p>
<p class="MsoNormal">clue mailing list: <a class="gmail-m_-4265875888698312093moz-txt-link-abbreviated" href="mailto:clue@cluedenver.org" target="_blank">clue@cluedenver.org</a></p>
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<p class="MsoNormal"><u></u> <u></u></p>
</div>
<br>
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