Bug 857530
| Summary: | Document lvmetad in 6.4, if deemed necessary for users | ||
|---|---|---|---|
| Product: | Red Hat Enterprise Linux 6 | Reporter: | Steven J. Levine <slevine> |
| Component: | doc-Logical_Volume_Manager | Assignee: | Steven J. Levine <slevine> |
| Status: | CLOSED CURRENTRELEASE | QA Contact: | ecs-bugs |
| Severity: | medium | Docs Contact: | |
| Priority: | high | ||
| Version: | 6.0 | CC: | agk, borgan, cmarthal, coughlan, djansa, dwysocha, heinzm, iannis, iheim, jbrassow, jha, jskeoch, ltroan, masaki.kimura.kz, mbroz, msnitzer, noboru.obata.ar, nperic, prajnoha, prockai, saguchi, ssaha, takahiro.yasui.mp, tyasui |
| Target Milestone: | beta | Keywords: | Documentation, FutureFeature |
| Target Release: | 6.3 | ||
| Hardware: | All | ||
| OS: | Linux | ||
| Whiteboard: | |||
| Fixed In Version: | Doc Type: | Enhancement | |
| Doc Text: | Story Points: | --- | |
| Clone Of: | 464877 | Environment: | |
| Last Closed: | 2013-02-25 18:30:41 UTC | Type: | --- |
| 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: | 464877 | ||
| Bug Blocks: | 464724, 697866, 705085, 718103, 756082 | ||
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Comment 3
Steven J. Levine
2012-10-10 00:11:21 UTC
Passed basic LVM tests with lvmetad/use_lvmetad turned on. Verifying as SanityOnly. lvm2-libs-2.02.98-2.el6.x86_64 lvm2-2.02.98-2.el6.x86_64 lvm2-cluster-2.02.98-2.el6.x86_64 device-mapper-1.02.77-2.el6.x86_64 device-mapper-libs-1.02.77-2.el6.x86_64 device-mapper-event-1.02.77-2.el6.x86_64 device-mapper-event-libs-1.02.77-2.el6.x86_64 cmirror-2.02.98-2.el6.x86_64 kernel-firmware-2.6.32-330.el6.noarch I'm re-opening this bug, since it is a doc bug and I need to be sure that the documentation is correct (and verified). Also the bug is assigned to me. Since I didn't have the information for this feature until after the development period I'm exceptioning this bug. I have a draft of what I have added to the LVM document that I will be sending to Petr for his ok. I have drafted the following text, presumably would work as a new section, 3.6 Metadata Daemon: LVM can optionally use a central metadata cache, implemented through a daemon (lvmetad) and an udev rule. The metadata daemon has two main purposes: it improves performance of LVM commands and it allows udev to automatically activate logical volumes or entire volume groups as they become available to the system. To take advantage of the daemon, it needs to be started through the "lvm2-lvmetad" service: use "chkconfig lvm2-lvmetad on" to start the daemon automatically at boot time, and "service lvm2-lvmetad start" to start it manually. Moreover, LVM needs to be configured to make use of the daemon. To this effect, set the lvm.conf variable "global/use_lvmetad" to 1. Normally, each LVM command issues a disk scan to find all relevant physical volumes and to read volume group metadata. However, if the metadata daemon is running and enabled, this expensive scan can be skipped: lvmetad scans each device only once, when it becomes available, via udev rules. Especially on systems with many disks, this can save significant amount of I/O and reduce the time required to complete LVM operations. When a new volume group is made available at runtime (eg. through hotplug or iSCSI), its logical volumes must be activated in order to be used. When lvmetad is enabled, the "activation/auto_activation_volume_list" lvm.conf option can be used to configure a list of volume groups and/or logical volumes that should be automatically activated. Without lvmetad, a manual activation is necessary. |