[linux-lvm] How to convert a single path to a multipath after using dm-multipath

[Giorgio Bersano]

Hi Zhiyong,
did you filter out the device in lvm.conf ?

filter = [ ... , "r/sd.*/" , ... ]

         or  "r/sda/" if you want to only exclude  sda

Regards,
Giorgio.


Il giorno gio 13 apr 2023 alle ore 08:55 Zhiyong Ye <yezhiyong at bytedance.com>
ha scritto:

>
> Hi Dave,
>
> Thank you for your reply.
>
> Because I had not considered multi-pathing before, there is no way to
> configure mpath on sda alone on the current stock of machines. And I
> tested this in my environment using lvchange --refresh, but it doesn't
> switch the active LV to use mpatha.
>
> # lvchange --refresh is-he57e6mr4wemb19kgf8i
> WARNING: Not using device /dev/mapper/mpatha for PV
> HgL3xR-qTio-m75Q-nGAO-Un0U-8uHk-wHbH25.
> WARNING: PV HgL3xR-qTio-m75Q-nGAO-Un0U-8uHk-wHbH25 prefers device
> /dev/sda because device is used by LV.
>
> # pvs
> WARNING: Not using device /dev/mapper/mpatha for PV
> HgL3xR-qTio-m75Q-nGAO-Un0U-8uHk-wHbH25.
> WARNING: PV HgL3xR-qTio-m75Q-nGAO-Un0U-8uHk-wHbH25 prefers device
> /dev/sda because device is used by LV.
> PV           VG                      Fmt  Attr PSize  PFree
> /dev/sda     is-he57e6mr4wemb19kgf8i lvm2 a--  10.00t 9.98t
>
> This is because duplicate PVs are encountered during the disk discovery
> phase, but lvmcache tends to use sda because it is currently being used
> by LV and mpatha will be dropped.
>
> I debugged the _choose_duplicates function in lvmcache and printed the
> following log:
> lvm[3352450]: PV HgL3xRqTiom75QnGAOUn0U8uHkwHbH25 compare duplicates:
> /dev/mapper/mpatha 254:3. /dev/sda 8:16. device_hint /dev/sda.
> vm[3352450]: PV HgL3xRqTiom75QnGAOUn0U8uHkwHbH25: size 21474836480.
> /dev/mapper/mpatha is 21474836480. /dev/sda is 21474836480.
> lvm[3352450]: PV HgL3xRqTiom75QnGAOUn0U8uHkwHbH25: /dev/mapper/mpatha
> was prev <none>. /dev/sda was prev <none>.
> lvm[3352450]: PV HgL3xRqTiom75QnGAOUn0U8uHkwHbH25: /dev/mapper/mpatha is
> in subsystem. /dev/sda is not in subsystem.
> lvm[3352450]: PV HgL3xRqTiom75QnGAOUn0U8uHkwHbH25: /dev/mapper/mpatha is
> dm. /dev/sda is not dm.
> lvm[3352450]: PV HgL3xRqTiom75QnGAOUn0U8uHkwHbH25: /dev/mapper/mpatha
> has no mounted fs. /dev/sda has no mounted fs.
> lvm[3352450]: PV HgL3xRqTiom75QnGAOUn0U8uHkwHbH25: /dev/mapper/mpatha is
> not used for LV. /dev/sda is used for LV.
> lvm[3352450]: PV HgL3xRqTiom75QnGAOUn0U8uHkwHbH25 with duplicates will
> change from /dev/mapper/mpatha to /dev/sda.
> lvm[3352450]: Dropping unchosen duplicate /dev/mapper/mpatha
> lvm[3352450]: Adding chosen duplicate /dev/sda
>
> Is there any way to change the PV preference policy in _choose_duplicates?
>
>




> Regards
>
> Zhiyong
>
> On 4/11/23 9:31 PM, David Teigland wrote:
> > On Tue, Apr 11, 2023 at 01:29:42PM +0800, Zhiyong Ye wrote:
> >> and lv on it. I then turn on the multipath function and merge the two
> paths
> >> into a new device (/dev/mapper/matha), and I get the following error
> when I
> >> execute the lvm command.
> >>
> >> # pvs
> >> WARNING: Not using device /dev/mapper/matha for PV
> >> HgL3xR-qTio-m75Q-nGAO-Un0U-8uHk-wHbH25.
> >> WARNING: PV HgL3xR-qTio-m75Q-nGAO-Un0U-8uHk-wHbH25 prefers device
> /dev/sda
> >> because device is used by LV.
> >> PV           VG                      Fmt  Attr PSize  PFree
> >> /dev/sda     is-he57e6mr4wemb19kgf8i lvm2 a--  10.00t 9.98t
> >
> >> May you please advise how one can convert the pv used by vg from sda to
> >> matha without affecting the current lv usage.
> >
> > lvchange --refresh should refresh the active LV to use mpatha.  To avoid
> > this, you might configure mpath on sda alone prior to adding the second
> > path.
> >
> > Dave
> >
>
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> read the LVM HOW-TO at http://tldp.org/HOWTO/LVM-HOWTO/
>
>
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