[linux-lvm] LVM fast mode

[linux-lvm] LVM fast mode

[Demi Marie Obenour]

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Would it be possible to have a fast, but less-safe mode for lvm2?
Right now lvm2 always enumerates every single block device on
the system, which is hugely wasteful when one knows exactly which
block devices are the PVs that will be affected by the operation.
“Less-safe” means that this is intended for use by programs that
know what they are doing, and that know that e.g. clustering is not
in use.  Using this in conjunction with clustering is a bug in the
application.  Commands that enumerate devices will, in fast mode, only
return LVs on the provided list of PVs.  Attempts to modify an LV on a
different PV would fail as of the LV did not exist.
-- 
Sincerely,
Demi Marie Obenour (she/her/hers)
Invisible Things Lab

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Re: [linux-lvm] LVM fast mode

[David Teigland]

On Mon, Mar 07, 2022 at 09:55:08AM -0500, Demi Marie Obenour wrote:
> Would it be possible to have a fast, but less-safe mode for lvm2?
> Right now lvm2 always enumerates every single block device on
> the system, which is hugely wasteful when one knows exactly which
> block devices are the PVs that will be affected by the operation.

You can do this by listing the PVs you know are needed with the --devices
option (or using a filter on older versions.)

> know what they are doing, and that know that e.g. clustering is not
> in use.  Using this in conjunction with clustering is a bug in the
> application.  

lvm won't be doing any cluster-related activity unless you have enabled
lvmlockd and have created a shared vg.

Dave
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