[linux-lvm] Saying goodbye to LVM
g.danti at assyoma.it
Wed Feb 7 21:19:28 UTC 2018
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
> 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
Hence my great interest in stratis...
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