Re: [gentoo-user] NAS and replacing with larger drives

[Frank Steinmetzger]

Am Sat, Dec 17, 2022 at 09:09:48AM -0700 schrieb Mark Knecht:

> On Sat, Dec 17, 2022 at 8:52 AM Dale <rdalek1967@×××××.com> wrote:

> > > I
> > > wonder, could one install the LVM stuff and use that?  That would be
> > > interesting.  I wonder if there is a NAS software that uses LVM
> > > instead.  Interesting thought.  I just may go bug google on that one.
> >
> > Maybe I'm missing the point but why would you want LVM on a
> > storage pool? If I'm doing backups I just want space. I let TrueNas
> > put it on disk and give it back if asked. Why put another layer
> > of indirection?
> > […]
> It's more about me being more used to using LVM.  Also, more used to
> Linux as well.  BSD is not something I have much experience with and until
> recently, none with ZFS.  Even the little experience I have with BSD was
> well over a decade ago, maybe two decades ago.  I barely remember it really.

The truenas interface is supposed to hide all that from you. As Mark wrote
two posts up, it’s an appliance. You install it once, that’s it. I think you
can install addons, but don’t have to. You maybe do updates once in a while,
perhaps not even that if it’s a critical production host. You don’t ssh into
it to do maintenance or to add or remove disks on the commandline. That’s
what the web UI is for. All of it. The biggest and most obvious difference
for me would be how devices are named in comparison to Linux.

> Hummm...I don't know Dale, I don't know... ZFS is a file system.
> LVM is an abstraction on top (or underneath?) of a file system.
> My understanding of LVM is that it frees you from hard decisions
> on partition sizes, not that it replaces ZFS or ext3/4/5.

LVM is “just” an abstraction layer between file system and storage. At the
bottom there are your block devices (drives, image files), which then may or
may not be RAIDed. Then you have LVM on top of that to encompass all those
devices into one big “virtual hard drive” and partition it (logical
volumes). And lastly you put file systems into those volumes. So there are
two, three (or even four, if you add encryption somewhere in between) layers
stacked onto your raw devices.

ZFS OTOH is all of that in one. It takes the raw block devices as a whole,
puts them (optionally) into redundancy structures, allows for “partitions”
(i.e. datasets) and lastly also *is* the file system. The advantage is that
it can combine its knowledge about all those layers to improve performance
and reliability. So for instance it distributes writes according to vdev
occupancy (LVM has no knowledge about the FS layer above it). Or when you
rebuild a RAID, only those parts that are actually used by the FS need to be
reconstructed, not the whole disk.

I may come off as a ZFS fanboy in this thread. But I am in no way an expert,
just a small-time user with just that one NAS with one RAID setup. That’s
it. I did a lot of reading beforehand, whether I should use it or mdadm or
btrfs. All my knowledge comes from that time, I never worked with it in my
professional life.

I also use LVM on my systems these days, just in case my root partition
becomes crowded and needs some extra space that I can take from the media
partition. Had to do this once, it went quick and was a fun experience.

> WRT you I recommend that you try living in NGL for a while. Possibly
> you are just a bit too indoctrinated in the religion of building packages
> 30-50 times a year believing (without hard data) that it provides value.

+1
I admit I like the occasional update of my Gentoo NAS. But that’s also
because it’s my last living Gentoo device. I always liked the environment,
still do. Gentoo was my first Linux after all, that stuff stays in your
mind. But oh the time-consuming hassle sometimes.

-- 
Grüße | Greetings | Salut | Qapla’
Please do not share anything from, with or about me on any social network.

The fantasy of men is often inadequate to grasp the reality of women.