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

[Zhiyong Ye]

Hi Giorgio,

Thank you for your reply and detailed answers.

When I filtered out the sda device on the lvm configuration file it 
works fine.

Thank you again for your help.

Regards

Zhiyong

On 4/13/23 6:54 PM, Giorgio Bersano wrote:
> 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 <mailto: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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