At Sat, 20 Dec 2025 09:26:30 +0100, Niels Dettenbach <[email protected]> wrote: Subject: Re: ZFS status on NetBSD > > > In practice, many use NetBSD UFS (or ext4 with linux) on ZFS zvol > volumes in virtualization environments like XEN (netbsd provides > xen dom0 as well - so it would make sense to have it). > > With UFS on hardware RAID you are far aeay from most of that - > even with sophisticated backup tools etc..
I have found that with true server hardware, with decent hardware RAID
implementations, such as the higher end of the Dell PERC series, that
NetBSD/Xen dom0 with plain LVM is by far the best performing way to
provide block storage to Xen domUs, especially while not having to
dedicate so much resources to the dom0.
While ZFS provides more features, it does so at the cost of internal
complexity where it tries to do all things for all purposes and thus
seems to suffer performance problems. It requires more CPU and RAM in
the dom0.
I also find ZFS is natively a bit more complex to configure and manage
with Xen than plain LVM LVs -- or maybe that's just because I've used
some form of LVM since a very long time ago (I started seeing it first
on AIX in the late 90s).
Now of course if you've got lower-end storage hardware without built-in
RAID functionality, or sub-standard RAID, and you really can benefit
from ZFS' ability to also be a RAID system, and you can afford the extra
RAM and CPU(s) dedicated to your dom0, then it will make sense to use
ZFS.
In terms of backups, well I just use a combination of rsync and
rdiff-backup to replicate my data to several different locations and I
manage that from each domU just as if it was a physical server. I've
never had the need to support live migration of domUs though (having to
do so seems like it must be the result of poor planning).
The one thing I'm really missing from NetBSD Xen domUs, at least on the
storage front, is the ability to have a shared directory with the dom0.
Xen provides all the tools and support to pass through 9p filesystems
(and as far as I can see it works in NetBSD dom0) but the NetBSD domU is
missing a way to see and mount them. (vio9p(4) provides this
functionality to QEMU, but it's tied to the virtio(4) bus -- we need a
xenbus(4) equivalent attachment for a 9p filesystem driver, and of
course also a similar vboxfs driver for virtualbox users.)
--
Greg A. Woods <[email protected]>
Kelowna, BC +1 250 762-7675 RoboHack <[email protected]>
Planix, Inc. <[email protected]> Avoncote Farms <[email protected]>
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