ZFS [Re: kldload vboxvfs.ko panics]

Michael Schuster michaelsprivate at gmail.com
Wed May 13 09:46:18 UTC 2020

Hi Christoph,

I'm changing the subject ... because the subject changed :-)

On Wed, May 13, 2020 at 10:11 AM Christoph Kukulies <kuku at kukulies.org>

> > yes ... sorry, should have mentioned that (ZFS is so embedded in my
> FreeBSD
> > "context", I always forget that some people don't use it yet).
> Can I catch  up to zfs quickly ?

I'm sure you can :-)

I don't have any links to online resources handy, I guess your fav. search
engine can produce those in sufficient number.

A few things I find relevant:

The very basic conceptual difference between ufs and zfs is that zfs is a
volume manager + file system all in one.
The basic "unit" zfs works in is a pool - the simplest pool consists of a
single disk, but the number of disks (and therefore the size of the storage
it offers) you can have in a pool is large (there are practical limits, but
the implementations don't impose any you'll reach in your life time ;-)).
Within a pool, you can arrange your disks in a stripe (ie, concatenated) or
mirrored, or as so-called "raidz"s with varying levels of parity, as well
as (reasonable) combinations thereof. Adding disks to existing pools is
easy; I haven't been following the effort to implement disk removal, that
seems to be a non-trivial effort (so think first before adding a disk you
can't spare ;-)).
(There are implications to how you organise your pools, esp. where pool
growth is concerned; though that's a complex topic in and of itself ...)

>From a pool, you can "carve out" any number of file systems. The neat thing
about this is that disk space in the pool is available to all file systems
until it's actually consumed, so you don't have to make hard decisions
about sizing when you create the FSs.

Creating a snapshot in zfs is very "cheap" (and fast).

Caveat: ZFS uses a lot of *virtual* addresses (or used to while I was at
Sun), so on a 32bit machine it may not be a good idea to try zfs (I don't
know whether it's even supported there).

AFAIK there's no ufs-to-zfs converter on the same disk, and if you want to
get some hands-on exposure before committing, I'd suggest you install
FreeBSD (or any Solaris derivative like illumos ;-)) with ZFS in a test
(virtual) machine first to get a feeling for it.

I hope that gives you an idea - I'm not the expert on ZFS by far, but if
you have questions and want to send them to me offline, feel free :-)

good luck!
Michael Schuster
recursion, n: see 'recursion'

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