[linux-lvm] Saying goodbye to LVM

[Gionatan Danti]

Il 07-02-2018 21:37 Xen ha scritto:
> This is the reason for the problems but LVM released bad products all
> the same with the solution being to not use them for very long, or
> rather, to upgrade.
> 
> Yes Ubuntu runs a long time behind and Debian also.
> 
> As a user, I can't help that, upgrading LVM just like that to have
> less "there is a pit here but we won't tell you about that" simply
> seems also fraught with peril.
> 
> For example, upgrading LVM slightly to 160 caused udev problems I
> didn't have before.
> 
> So you can blame the distributions, you can also blame features being
> released first and proper protection only being added much later.
> 
> So if you're on Xenial, you are stuck with the features but without
> the protection.
> 
> In particular there is a quagmire of situations you can end up with
> wrt the shielding and dual activation of the same vg, many times of
> which you can only get out of the situation with dmsetup remove, but I
> didn't know this at first.
> 
> Or you end up in the situation where a PV is missing and you cannot
> edit the VG, but in order to remove the PV you have to edit the VG.
> 
> A missing cache device cannot be removed without the missing cache
> device being present.
> 
> I meant to say, you can have 2 disks out of sync and resolving it is
> not possible other than by editing config on disk and doing
> vgcfgrestore.
> 
> But you can't do vgcfgrestore without removing a missing PV first.
> 
> There is a huge amount of chicken and egg problems because physically
> a VG sits inside a PV but logically a PV sits inside a VG and this
> constantly causes issues.
> 
> LVM just has conceptual problems.

As a CentOS user, I *never* encountered such problems. I really think 
these are caused by the lack of proper integration testing from 
Debian/Ubuntu. But hey - all key LVM developers are RedHat people, so it 
should be expected (for the better/worse).

I can not say anything about lvmcache, though.

> 
> I cannot write more yet because I don't have ZFS setup yet.
> 
> I don't like ZFS too much because it's opaque and Linux support seems
> to be flimsy (for example boot support) and the only good
> documentation is Oracle but it often does not apply.

True. I never use it with boot device. LVM and XFS are, on the other 
hand, extremely well integrated into mainline kernel/userspace 
utilities.

Hence my great interest in stratis...
Regards.

-- 
Danti Gionatan
Supporto Tecnico
Assyoma S.r.l. - www.assyoma.it
email: g.danti at assyoma.it - info at assyoma.it
GPG public key ID: FF5F32A8