Bug 1676598
| Summary: | Switch the default of "scanning LVs for LVM labels" from 'on' to 'off' | ||
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| Product: | Red Hat Enterprise Linux 8 | Reporter: | Jonathan Earl Brassow <jbrassow> |
| Component: | lvm2 | Assignee: | David Teigland <teigland> |
| lvm2 sub component: | Devices, Filtering and Stacking | QA Contact: | cluster-qe <cluster-qe> |
| Status: | CLOSED CURRENTRELEASE | Docs Contact: | |
| Severity: | unspecified | ||
| Priority: | unspecified | CC: | agk, cmarthal, heinzm, jbrassow, mcsontos, msnitzer, prajnoha, rhandlin, slevine, wchadwic, zkabelac |
| Version: | 8.0 | ||
| Target Milestone: | rc | ||
| Target Release: | 8.0 | ||
| Hardware: | Unspecified | ||
| OS: | Unspecified | ||
| Whiteboard: | |||
| Fixed In Version: | lvm2-2.03.02-6.el8 | Doc Type: | Enhancement |
| Doc Text: |
.New `scan_lvs` configuration setting
A new `lvm.conf` configuration file setting, `scan_lvs`, has been added and set to 0 by default. The new default behavior stops LVM from looking for PVs that may exist on top of LVs; that is, it will not scan active LVs for more PVs. The default setting also prevents LVM from creating PVs on top of LVs.
Layering PVs on top of LVs can occur by way of VM images placed on top of LVs, in which case it is not safe for the host to access the PVs. Avoiding this unsafe access is the primary reason for the new default behavior. Also, in environments with many active LVs, the amount of device scanning done by LVM can be significantly decreased.
The previous behavior can be restored by changing this setting to 1.
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Story Points: | --- |
| Clone Of: | 1674563 | Environment: | |
| Last Closed: | 2019-06-13 22:52:52 UTC | Type: | Bug |
| Regression: | --- | Mount Type: | --- |
| Documentation: | --- | CRM: | |
| Verified Versions: | Category: | --- | |
| oVirt Team: | --- | RHEL 7.3 requirements from Atomic Host: | |
| Cloudforms Team: | --- | Target Upstream Version: | |
| Embargoed: | |||
| Bug Depends On: | 1674563 | ||
| Bug Blocks: | |||
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Description
Jonathan Earl Brassow
2019-02-12 16:10:02 UTC
I believe we can save our support organization a lot of headaches by making this change. I've spoken with the GSS team and they agree that making this default change would save them a lot of calls and trouble. We are in the process of changing this default value for the next RHEL7 minor release. If we can't make this change in RHEL8.0, we would certainly do it in RHEL8.1. It would be a shame if we could not start out RHEL8 with the defaults the way we have recently learned would provide the most benefit. Marking verified in the latest rpms.
kernel-4.18.0-71.el8 BUILT: Fri Feb 22 17:00:18 CST 2019
lvm2-2.03.02-6.el8 BUILT: Fri Feb 22 04:47:54 CST 2019
lvm2-libs-2.03.02-6.el8 BUILT: Fri Feb 22 04:47:54 CST 2019
device-mapper-1.02.155-6.el8 BUILT: Fri Feb 22 04:47:54 CST 2019
device-mapper-libs-1.02.155-6.el8 BUILT: Fri Feb 22 04:47:54 CST 2019
device-mapper-event-1.02.155-6.el8 BUILT: Fri Feb 22 04:47:54 CST 2019
device-mapper-event-libs-1.02.155-6.el8 BUILT: Fri Feb 22 04:47:54 CST 2019
device-mapper-persistent-data-0.7.6-1.el8 BUILT: Sun Aug 12 04:21:55 CDT 2018
# LV PV create attempt
[root@hayes-02 lvm]# pvcreate -y --config devices/scan_lvs=0 /dev/snapper_thinp/snap_level1
Device /dev/snapper_thinp/snap_level1 excluded by a filter.
[root@hayes-02 lvm]# pvcreate -y --config devices/scan_lvs=1 /dev/snapper_thinp/snap_level1
Physical volume "/dev/snapper_thinp/snap_level1" successfully created.
# LV VG create attempt
[root@hayes-02 lvm]# vgcreate STACK /dev/snapper_thinp/snap_level1
Device /dev/snapper_thinp/snap_level1 excluded by a filter.
[root@hayes-02 lvm]# vgcreate STACK --config devices/scan_lvs=1 /dev/snapper_thinp/snap_level1
Volume group "STACK" successfully created
# LV stacked on LV create attempt
[root@hayes-02 lvm]# lvcreate -L 100m STACK
Volume group "STACK" not found
Cannot process volume group STACK
[root@hayes-02 lvm]# lvcreate --config devices/scan_lvs=1 -L 100m STACK
Logical volume "lvol0" created.
# lvs display
[root@hayes-02 lvm]# lvs -a -o +devices
LV VG Attr LSize Pool Origin Data% Meta% Devices
POOL snapper_thinp twi-aotz-- 1.00g 0.02 11.62 POOL_tdata(0)
[POOL_tdata] snapper_thinp Twi-ao---- 1.00g /dev/sdl1(1)
[POOL_tmeta] snapper_thinp ewi-ao---- 4.00m /dev/sdn1(0)
[lvol0_pmspare] snapper_thinp ewi------- 4.00m /dev/sdl1(0)
origin snapper_thinp Vwi-a-tz-- 1.00g POOL 0.00
snap_level1 snapper_thinp Vwi-aotz-- 1.00g POOL origin 0.02
[root@hayes-02 lvm]# lvs --config devices/scan_lvs=1 -a -o +devices
LV VG Attr LSize Pool Origin Data% Meta% Devices
lvol0 STACK -wi-a----- 100.00m /dev/snapper_thinp/snap_level1(0)
POOL snapper_thinp twi-aotz-- 1.00g 0.02 11.62 POOL_tdata(0)
[POOL_tdata] snapper_thinp Twi-ao---- 1.00g /dev/sdl1(1)
[POOL_tmeta] snapper_thinp ewi-ao---- 4.00m /dev/sdn1(0)
[lvol0_pmspare] snapper_thinp ewi------- 4.00m /dev/sdl1(0)
origin snapper_thinp Vwi-a-tz-- 1.00g POOL 0.00
snap_level1 snapper_thinp Vwi-aotz-- 1.00g POOL origin 0.02
# vgs display
[root@hayes-02 lvm]# vgs
VG #PV #LV #SN Attr VSize VFree
snapper_thinp 5 8 0 wz--n- 2.18t <2.18t
[root@hayes-02 lvm]# vgs --config devices/scan_lvs=1
VG #PV #LV #SN Attr VSize VFree
STACK 1 1 0 wz--n- 1020.00m 920.00m
snapper_thinp 5 8 0 wz--n- 2.18t <2.18t
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