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

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

[Zhiyong Ye]

Dear all,

Dm-multipath (multipath-tools in the user-space) provides powerful 
multipathing capabilities to aggregate multiple paths from the same 
storage backend into a single disk device. However, it is difficult to 
extend single paths into multipaths when LVM is already in use.

I used two physical machines to set up the POC environment for testing, 
with one physical machine acting as the storage iscsi multipath server, 
setting up the same LUN to have two paths to access. Another physical 
machine acts as the iscsi client, first using a single path (/dev/sda) 
and creating vg 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


To be able to use the multipathing capability, I tried to convert the 
device from pv to matha using vgimportclone, but it failed since both 
sda and matha were pointing to the same iscsi storage backend.

May you please advise how one can convert the pv used by vg from sda to 
matha without affecting the current lv usage.

Regards

Zhiyong

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

[David Teigland]

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

[Zhiyong Ye]

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

[Giorgio Bersano]

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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@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
> >
>
> _______________________________________________
> linux-lvm mailing list
> linux-lvm@redhat.com
> https://listman.redhat.com/mailman/listinfo/linux-lvm
> read the LVM HOW-TO at http://tldp.org/HOWTO/LVM-HOWTO/
>
>

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_______________________________________________
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read the LVM HOW-TO at http://tldp.org/HOWTO/LVM-HOWTO/

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

[David Teigland]

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
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Re: [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@bytedance.com <mailto:yezhiyong@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
>      >
> 
>     _______________________________________________
>     linux-lvm mailing list
>     linux-lvm@redhat.com <mailto:linux-lvm@redhat.com>
>     https://listman.redhat.com/mailman/listinfo/linux-lvm
>     <https://listman.redhat.com/mailman/listinfo/linux-lvm>
>     read the LVM HOW-TO at http://tldp.org/HOWTO/LVM-HOWTO/
>     <http://tldp.org/HOWTO/LVM-HOWTO/>
> 

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Re: [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
> 

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