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

[Zhiyong Ye]

Hi Dave,

Thank you for your patience and explanations.

When I filtered out the sda device on the lvm configuration file it 
works fine. I will test it again with the latest version of lvm and 
compare which patches have been added.

I learned a lot from our discussions and thank you again for your help.

Regards

Zhiyong

On 4/14/23 4:28 AM, David Teigland wrote:
> On Wed, Apr 12, 2023 at 05:16:41PM +0800, Zhiyong Ye wrote:
>> 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.
> 
> It seems to work for me with the latest version of lvm, which may be due
> to improved multipath component detection and/or improved handling of
> duplicate PVs.  So the current upstream code might work for you also.
> 
> # pvs
>    PV         VG           Fmt  Attr PSize    PFree
>    /dev/sdf   ff           lvm2 a--  <931.01g <930.76g
> 
> # lvs -o+devices
>    LV    VG           Attr       LSize    Origin Devices
>    lvol1 ff           -wi-ao----  256.00m        /dev/sdf(1)
> 
> # mount | grep ff
> /dev/mapper/ff-lvol1 on /mnt type xfs (rw,relatime,seclabel,attr2,inode64,logbufs=8,logbsize=32k,noquota)
> 
> # multipath -a /dev/sdf
> wwid '3690b11c0000438ad0000057150910423' added
> 
> # multipath -l
> mpatha (3690b11c0000438ad0000057150910423) dm-4 DELL,MD32xxi
> size=931G features='2 pg_init_retries 50' hwhandler='1 rdac' wp=rw
> `-+- policy='service-time 0' prio=0 status=active
>    `- 7:0:0:4 sdf 8:80 active undef running
> 
> # pvs
>    WARNING: Device mismatch detected for ff/lvol1 which is accessing /dev/sdf instead of /dev/mapper/mpatha.
>    PV                 VG           Fmt  Attr PSize    PFree
>    /dev/mapper/mpatha ff           lvm2 a--  <931.01g <930.76g
> 
> # lvs ff
>    WARNING: Device mismatch detected for ff/lvol1 which is accessing /dev/sdf instead of /dev/mapper/mpatha.
>    LV    VG Attr       LSize
>    lvol1 ff -wi-ao---- 256.00m
> 
> # dmsetup table ff-lvol1
> 0 524288 linear 8:80 10240
> 
> # lvchange --refresh ff/lvol1
> 
> # dmsetup table ff-lvol1
> 0 524288 linear 253:4 10240
> 
> # pvs
>    PV                 VG           Fmt  Attr PSize    PFree
>    /dev/mapper/mpatha ff           lvm2 a--  <931.01g <930.76g
> 
> # lvs -o+devices ff
>    LV    VG Attr       LSize   Devices
>    lvol1 ff -wi-ao---- 256.00m /dev/mapper/mpatha(1)
> 
> Dave
>