On 11/17/2018 10:53 AM, Predrag Punosevac wrote:
On Sat, Nov 17, 2018 at 01:35:05AM +0100, Willi Rauffer wrote:
Hello,
we want to make one logical volume out of several physical volumes, but there
is no \
LVM (Logical Volume Manager) in OpenBSD!
Will there be a LVM in OpenBSD in the future?
Thanks...Willi Rauffer, UNOBank.org
There are people on this mailing list infinitely more knowledgeable and
experienced than I both with Linux and BSDs so they will correct me
claims if necessary.
In my experience using LVM2 (LVM is depreciated) to create software RIAD
even on Linux (I have the most experience with RHEL) is a bad idea
unless you belive at the RedHat PR BS. Most people myself included if
they have to use softraid on Linux prefer to do it from mdadm (softraid
discipline for Linux and then perhaps put LVM on the top of it although
I fail to see the purpose). In the lieu of the lack of modern file
system on Linux (Btrfs is a vaporware and ZFS is an external kernel
module which lags many version numbers behind Solaris and FreeBSD) some
PR guys from RedHat started even advertising LVM2 snapshots as a real
snapshots. That is pure BS as they are very expensive operation and for
all practical purposes useless on the legacy file system XFS which is
really the only really stable FS on Linux. If you are storing your data
on Linux you should be using Hardware RAID and XFS.
Not having LVM2 on OpenBSD is a feature not a bug! Dragon Fly BSD has
partial not really functional implementation of LVM that I am quite
familiar with. IIRC NetBSD has LVM2 implementation but it is hard to me
to say usefulness of it as I have never used.
As somebody mentioned. OpenBSD softraid can be used to manage logical
volumes
oko# bioctl softraid0
Volume Status Size Device
softraid0 0 Online 2000396018176 sd3 RAID1
0 Online 2000396018176 0:0.0 noencl <sd0a>
1 Online 2000396018176 0:1.0 noencl <sd1a>
but it is quite crude and it will take you more than a week to rebuild
simple 10 TB mirror. IMHO softraid is far more useful for drive
encryption on your laptop for example than for data storage. I don't
have any experience with Hardware RAID cards on OpenBSD (Areca should
have really good support) which I do prefer over softraid (but not over
ZFS). However OpenBSD lacks modern file system (read HAMMER or HAMMER2)
to take advantage of such set up.
Best,
Predrag
P.S. OpenBSD's NFSv3 server and client implementation is pretty slow so
that begs the question how you are going to access that data pool.
I concur, software raid is a bug, not a feature, especially since if you
truly need RAID, hardware cards are fairly cheap. But if you can't
afford such a card, fairly reliable method is to just replicate the
/altroot scheme with all your partitions. Even just using an external
drive that you do periodic backups to is more reliable than software
raid. For the most part, I've actually seen more failures with softraid
than just independent disk even between systems where the only
difference is the serial number being slightly incremented (sofraid, no
matter how well coded still causes far more disk usage than a normal
un-raided disk).
Although, really, if you need reliability, it is much cheaper, less
effort intensive, and more reliable to just grab a bunch of low-end
systems and cluster them together. I have a small cluster 5 crusty old
SunFire V120 boxes that've been running OpenBSD for nearly 10 years as
my firewalls, I'm just running with a single disk in each. Each of them
has failed at least a couple items over the years (failed disks, RAM
modules, motherboards, power supplies, etc), but collectively they've
had 100% reliability, even counting time for required reboots for
upgrades, patches, and other maintenance
Overall, I've found that software raid systems are only good for
supporting whole-disk crypto and nothing else. Otherwise you are just
adding an unnecessary performance penalty, kills your disks faster, and
makes it much more a pain in the ass to recover from.
-C
.
