Re: [linux-lvm] Why does every lvm command insist on touching every pv?

[Takahiro Yasui <tyasui@redhat.com>]

On 06/15/10 16:24, Phillip Susi wrote:
> On 6/15/2010 3:17 PM, Takahiro Yasui wrote:
>> Everytime lvm command is executed, all PVs are accessed.
>>
>> This is a known issue and what we should fix. If there are a lot of
>> PVs, execution of lvm command could take a long time. The scan also
>> affects error recovery time of lvm mirror.
>>
>> This is an old reference.
>>
>> Introduce metadata cache feature
>> https://www.redhat.com/archives/lvm-devel/2009-April/msg00014.html
> 
> This seems to limit the number of metadata copies on pvs that are
> accessed to one, but I am seeing even block devices that are not pvs
> accessed, like it is scanning for new pvs.  This patch seems like it
> would help some though, but it is over a year old.  Did it never get
> applied?

As for accessing block devices, you can limit accesses to those
devices by filter option in lvm.conf. This is an example which
allows accesses only to /dev/sd*

    filter = [ "a|/dev/sd|", "r|.*|" ]

You can specify more strict rule like

    filter = [ "a|/dev/sd[a-z]|", "r|.*|" ]

For my patch, I posted it one year ago but I need to have more
discussion how to solve this issue on lvm-devel.

Thanks,
Taka