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man lvmlockd: add section about first sanlock VG

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Add a section specifically about creating the first
sanlock VG.
This commit is contained in:
David Teigland 2015-09-04 13:01:03 -05:00
parent 869c0bdeb8
commit 43d6b5b375
1 changed files with 34 additions and 11 deletions
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45
man/lvmlockd.8.in
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@ -298,6 +298,32 @@ LVM commands request locks from clvmd to use the VG.
.P
.SS creating the first sanlock VG
Creating the first sanlock VG is not protected by locking and requires
special attention. This is because sanlock locks exist within the VG, so
they are not available until the VG exists. The first sanlock VG will
contain the "global lock".
.IP \[bu] 2
While running vgcreate for the first sanlock VG, ensure that the PV being
used is not used by another LVM command. Allocation of shared PVs is
usually protected by the global lock, but this cannot be done for the
first sanlock VG which will hold the global lock.
.IP \[bu] 2
While running vgcreate for the first sanlock VG, ensure that the VG name
being used is not used by another LVM command. Uniqueness of VG names is
usually ensured by the global lock.
.IP \[bu] 2
Because the first sanlock VG will contain the global lock, this VG needs
to be accessible to all hosts that will use sanlock shared VGs. All hosts
will need to use the global lock from the first sanlock VG.
See below for other special cases related to moving the global lock.
.SS using lockd VGs
There are some special considerations when using lockd VGs.
@ -479,9 +505,7 @@ global/lvmlockd_lock_retries before failing. If a request for an LV lock
fails due to a lock conflict, the command fails immediately.
.SS sanlock global lock
There are some special cases related to the global lock in sanlock VGs.
.SS managing the global lock in sanlock VGs
The global lock exists in one of the sanlock VGs. The first sanlock VG
created will contain the global lock. Subsequent sanlock VGs will each
@ -526,14 +550,7 @@ A small sanlock VG dedicated to holding the global lock can avoid the case
where the GL lock must be manually enabled after a vgremove.
.SS sanlock VG usage
There are some special cases related to using a sanlock VG.
vgremove of a sanlock VG will fail if other hosts have the VG started.
Run vgchange \-\-lock-stop <vgname> on all other hosts before vgremove.
(It may take several seconds before vgremove recognizes that all hosts
have stopped.)
.SS internal lvmlock LV
A sanlock VG contains a hidden LV called "lvmlock" that holds the sanlock
locks. vgreduce cannot yet remove the PV holding the lvmlock LV. To
@ -543,6 +560,12 @@ change the VG lock type back to "sanlock".
To place the lvmlock LV on a specific device, create the VG with only that
device, then use vgextend to add other devices.
vgremove of a sanlock VG will fail if other hosts have the VG started.
Run vgchange \-\-lock-stop <vgname> on all other hosts before vgremove.
(It may take several seconds before vgremove recognizes that all hosts
have stopped.) This is necessary because while a host has a sanlock VG
started, it is using the internal lvmlock LV.
.SS shared LVs