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@assyoma.it - info@assyoma.it GPG public key ID: FF5F32A8 _______________________________________________ linux-lvm mailing list linux-lvm@redhat.com https://www.redhat.com/mailman/listinfo/linux-lvm read the LVM HOW-TO at http://tldp.org/HOWTO/LVM-HOWTO/
