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Chapter 61. Storage

LVM does not support event-based autoactivation of incomplete volume groups

If a volume group is not complete and physical volumes are missing, LVM does not support automatic LVM event-based activation of that volume group. This implies a setting of --activationmode complete whenever autoactivation takes place. For information on the --activationmode complete option and automatic activation, see the vgchange(8) and pvscan(8) man pages.
Note that the event-driven autoactivation hooks are enabled when lvmetad is enabled with the global/use_lvmetad=1 setting in the /etc/lvm/lvm.conf configuration file. Also note that without autoactivation, there is a direct activation hook at the exact time during boot at which the volume groups are activated with only the physical volumes that are available at that time. Any physical volumes that appear later are not taken into account.
This issue does not affect early boot in initramfs (dracut) nor does this affect direct activation from the command line using vgchange and lvchange calls, which default to degraded activation mode. (BZ#1337220)

The vdo service is disabled after upgrading to Red Hat Enterprise Linux 7.6

Upgrading from Red Hat Enterprise Linux 7.5 to 7.6 disables the vdo service if it was previously enabled. This is because of missing systemd macros in the vdo RPM package.
The problem has been fixed in the 7.6 release, and upgrading from Red Hat Enterprise Linux 7.6 to a later release will no longer disable vdo. (BZ#1617896)

Data corruption occurs on RAID 10 reshape on top of VDO.

RAID 10 reshape (with both LVM and mdadm) on top of VDO corrupts data. Stacking RAID 10 (or other RAID types) on top of VDO does not take advantage of the deduplication and compression capabilities of VDO and is not recommended. (BZ#1528466, BZ#1530776)

System boot is sometimes delayed by ndctl

A udev rule installed by the ndctl package sometimes delays the system boot process for several minutes on systems with Non-Volatile Dual In-line Memory Module (NVDIMM) devices. In such cases, systemd displays a message similar to the following:
INFO: task systemd-udevd:1554 blocked for more than 120 seconds.
nvdimm_bus_check_dimm_count+0x31/0xa0 [libnvdimm]
To work around the issue, disable the udev rule using the following command:
# rm /usr/lib/udev/rules.d/80-ndctl.rules
After disabling the udev rule, the described problem no longer occurs. (BZ#1635441)

LVM might cause data corruption in the first 128kB of allocatable space of a physical volume

A bug in the I/O layer of LVM causes LVM to read and write back the first 128kB of data that immediately follows the LVM metadata on the disk. If another program or the file system is modifying these blocks when you use an LVM command, changes might be lost. As a consequence, this might lead to data corruption in rare cases.
To work around this problem, avoid using LVM commands that change volume group (VG) metadata, such as lvcreate or lvextend, while logical volumes (LVs) in the VG are in use. (BZ#1643651)