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man: add info to lvmsystemid

about losing access to a VG if lvm is downgraded
to an earlier version.
This commit is contained in:
David Teigland 2015-03-05 12:12:42 -06:00
parent 5e25bca1a9
commit b48ff3b94e

View File

@ -42,13 +42,7 @@ maximum length of a system_id is 128 characters.
To benefit fully from system_id, all hosts must have system_id set, and
VGs must have system_id set. A VG on shared storage can be damaged or
destroyed in the following cases which the user must be careful to avoid:
.IP \[bu] 2
A host using an old version of lvm without the system_id feature will not
recognize the system_id of other hosts' VGs. VGs with a new system_id
are nominally protected from old versions of lvm by appearing to be
read-only to the old versions.
destroyed in some cases which the user must be careful to avoid.
.IP \[bu] 2
A VG without a system_id can be used without restriction from any host,
@ -73,6 +67,19 @@ operations and corrupting the PVs. See the
.B orphans
section for more information.
.IP \[bu] 2
A host using an old version of lvm without the system_id feature will not
recognize a new system_id in VGs from other hosts. Even though the old
version of lvm is not blocked from reading a VG with a system_id, it is
blocked from writing to the VG (or its LVs). The new system_id changes
the write mode of a VG, making it appear read-only to previous lvm
versions.
This also means that if a host downgrades its version of lvm, it would
lose access to any VGs it had created with a system_id. To avoid this,
the system_id should be removed from VGs before downgrading to an lvm
version without the system_id feature.
.P
.SS Types of VG access