[ClusterLabs] Antw: Stupid DRBD/LVM Global Filter Question

Ulrich Windl Ulrich.Windl at rz.uni-regensburg.de
Wed Oct 30 09:11:21 EDT 2019

>>> Eric Robinson <eric.robinson at psmnv.com> schrieb am 29.10.2019 um 23:17 in
<MN2PR03MB4845E1FBC259A2B29176FC33FA610 at MN2PR03MB4845.namprd03.prod.outlook.com>

> If I have an LV as a backing device for a DRBD disk, can someone explain why

> I need an LVM filter? It seems to me that we would want the LV to be always

> active under both the primary and secondary DRBD devices, and there should
> no need or desire to have the LV activated or deactivated by Pacemaker. What

> am I missing?

At least in the past it also had a performance reason: Most LVM tools did not
cache device information, and instead did O_DIRECT device access. In a SAN
environment with more than 100 disk paths, plus device-mapper devices,
partitions, etc. The delay and I/O impact was significant. So if you are using
LVM only on a few devices, help LVM to locate those. Also for multipath you
want LVM to use the multipath device instead of a single path device for


> ‑‑Eric
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