Re: [linux-lvm] LVM preference for multipath verses disk/by-id/scsi

[brem belguebli <brem.belguebli@gmail.com>]

Hi,

see man 5 lvm.conf there is an option called preferred_names which is
well explained

It'll instruct lvm to use the preferred_names you configured in the
lvm.conf file if they exist

ie : preferred_names = "/dev/mpath/" will use /dev/mpath/XXX instead
of /dev/mapper/XXX


2009/12/30 Simon Loewenthal/NL/Tele2 <simon.loewenthal@tele2.com>:
> I don't think this original Email made it through to the list, but I
> think I have found an solution:
>
> In lvm.conf there is this line,
> filter = [ "r|/dev/.*/by-path/.*|", "r|/dev/.*/by-id/.*|", "a/.*/" ]
>
> If I remove the portion "r|/dev/.*/by-id/.*|", so it is rewritten as,
> filter = [ "r|/dev/.*/by-path/.*|", "a/.*/" ]
> ...then it ought to ignore the device,
> /dev/disk/by-id/scsi-360060480000290300618533030313133
>
> Is this correct?
>
> S.
>
> --
> Simon Loewenthal/Tele2
>
>
> Simon Loewenthal/NL/Tele2 wrote:
>> Dear all,
>>
>> � � I have a volume group that is currently using discs directly
>> presented from EMC e.g
>> /dev/disk/by-id/scsi-360060480000290300618533030313042 .
>>
>> An lvdisplay -v shows these PVs:
>> # vgdisplay -v vg_mds
>> � � Using volume group(s) on command line
>> � � Finding volume group "vg_mds"
>> � --- Volume group ---
>> � VG Name � � � � � � � vg_mds
>> � System ID
>> � Format � � � � � � � �lvm2
>> � Metadata Areas � � � �12
>> � Metadata Sequence No �4
>> � VG Access � � � � � � read/write
>> � VG Status � � � � � � resizable
>> � MAX LV � � � � � � � �0
>> � Cur LV � � � � � � � �1
>> � Open LV � � � � � � � 1
>> � Max PV � � � � � � � �0
>> � Cur PV � � � � � � � �12
>> � Act PV � � � � � � � �12
>> � VG Size � � � � � � � 202.12 GB
>> � PE Size � � � � � � � 32.00 MB
>> � Total PE � � � � � � �6468
>> � Alloc PE / Size � � � 6468 / 202.12 GB
>> � Free �PE / Size � � � 0 / 0
>> � VG UUID � � � � � � � Wnk1a8-xdVf-RorP-ZxPE-Z3D9-5fp1-2o4hHs
>>
>> � --- Logical volume ---
>> � LV Name � � � � � � � �/dev/vg_mds/lvol_mds
>> � VG Name � � � � � � � �vg_mds
>> � LV UUID � � � � � � � �TErCZW-senu-YR3k-I25n-Tqk9-BK2k-3mQY3S
>> � LV Write Access � � � �read/write
>> � LV Status � � � � � � �available
>> � # open � � � � � � � � 1
>> � LV Size � � � � � � � �202.12 GB
>> � Current LE � � � � � � 6468
>> � Segments � � � � � � � 12
>> � Allocation � � � � � � inherit
>> � Read ahead sectors � � 0
>> � Block device � � � � � 253:7
>>
>> � --- Physical volumes ---
>> � PV Name
>> /dev/disk/by-id/scsi-360060480000290300618533030313133
>> � PV UUID � � � � � � � 255V1X-uMZp-Lod1-3jsa-cCGd-JaNZ-v0dEXn
>> � PV Status � � � � � � allocatable
>> � Total PE / Free PE � �539 / 0
>>
>> � PV Name
>> /dev/disk/by-id/scsi-360060480000290300618533030313131
>> � PV UUID � � � � � � � RU5WZK-G3hY-lXCD-F6Kj-PcJA-DcbE-iV17P7
>> � PV Status � � � � � � allocatable
>> � Total PE / Free PE � �539 / 0
>>
>> � PV Name
>> /dev/disk/by-id/scsi-360060480000290300618533030313046
>> � PV UUID � � � � � � � c3DVym-lzdw-MgS6-acQI-BcUD-UOGq-iG6hSe
>> � PV Status � � � � � � allocatable
>> � Total PE / Free PE � �539 / 0
>>
>> � PV Name
>> /dev/disk/by-id/scsi-360060480000290300618533030313044
>> � PV UUID � � � � � � � d7VD54-KmXZ-t8eX-dvph-9lSp-ym03-Lc62sI
>> � PV Status � � � � � � allocatable
>> � Total PE / Free PE � �539 / 0
>>
>> � PV Name
>> /dev/disk/by-id/scsi-360060480000290300618533030313042
>> � PV UUID � � � � � � � n32oAY-soe3-odYI-SAFQ-yM7v-FRaw-e9hS63
>> � PV Status � � � � � � allocatable
>> � Total PE / Free PE � �539 / 0
>>
>> � PV Name
>> /dev/disk/by-id/scsi-360060480000290300618533030313039
>> � PV UUID � � � � � � � hT2hZ7-XAZr-ZUte-rzLV-kwFX-Jtih-K3OgZe
>> � PV Status � � � � � � allocatable
>> � Total PE / Free PE � �539 / 0
>>
>> � PV Name
>> /dev/disk/by-id/scsi-360060480000290300618533030313037
>> � PV UUID � � � � � � � ut4fEx-R0c2-lA4y-qS3F-SYfp-Chuz-2SrvTo
>> � PV Status � � � � � � allocatable
>> � Total PE / Free PE � �539 / 0
>>
>> � PV Name
>> /dev/disk/by-id/scsi-360060480000290300618533030313035
>> � PV UUID � � � � � � � BMJ8LA-b0L7-aAoK-4WqG-MLdU-s8Y8-xGib2s
>> � PV Status � � � � � � allocatable
>> � Total PE / Free PE � �539 / 0
>>
>> � PV Name
>> /dev/disk/by-id/scsi-360060480000290300618533030313033
>> � PV UUID � � � � � � � uSasZ1-96rT-ngGN-Wfcr-fBNg-ceM0-GaccVU
>> � PV Status � � � � � � allocatable
>> � Total PE / Free PE � �539 / 0
>>
>> � PV Name
>> /dev/disk/by-id/scsi-360060480000290300618533030313031
>> � PV UUID � � � � � � � R15yAf-t1YO-Z0Dx-4n2G-oTyD-Secp-2igMJc
>> � PV Status � � � � � � allocatable
>> � Total PE / Free PE � �539 / 0
>>
>> � PV Name
>> /dev/disk/by-id/scsi-360060480000290300618533030304646
>> � PV UUID � � � � � � � nrhhx1-7AxM-VmVv-sRY5-TLR7-UAEE-wBUIMB
>> � PV Status � � � � � � allocatable
>> � Total PE / Free PE � �539 / 0
>>
>> � PV Name
>> /dev/disk/by-id/scsi-360060480000290300618533030304644
>> � PV UUID � � � � � � � ctz8rd-ew58-0pU8-FssR-x9pR-KSA9-mI4flw
>> � PV Status � � � � � � allocatable
>> � Total PE / Free PE � �539 / 0
>>
>>
>> I want to export this volume group and inport it again using
>> multipathing. �I have configured the multipathing thus,
>> �# multipath -ll
>> dm-6_010F (360060480000290300618533030313046) dm-6 EMC,SYMMETRIX
>> [size=17G][features=0][hwhandler=0]
>> \_ round-robin 0 [prio=2][active]
>> �\_ 0:0:0:31 sdx � � � �65:112 [active][ready]
>> �\_ 1:0:0:31 sdk � � � �8:160 �[active][ready]
>> dm-17_0012 (360060480000290300618533030303132) dm-17 EMC,SYMMETRIX
>> [size=4.7M][features=0][hwhandler=0]
>> \_ round-robin 0 [prio=2][active]
>> �\_ 0:0:0:0 �sdn � � � �8:208 �[active][ready]
>> �\_ 1:0:0:0 �sda � � � �8:0 � �[active][ready]
>> dm-13_0103 (360060480000290300618533030313033) dm-13 EMC,SYMMETRIX
>> [size=17G][features=0][hwhandler=0]
>> \_ round-robin 0 [prio=2][active]
>> �\_ 0:0:0:25 sdr � � � �65:16 �[active][ready]
>> �\_ 1:0:0:25 sde � � � �8:64 � [active][ready]
>> dm-10_0109 (360060480000290300618533030313039) dm-10 EMC,SYMMETRIX
>> [size=17G][features=0][hwhandler=0]
>> \_ round-robin 0 [prio=2][active]
>> �\_ 0:0:0:28 sdu � � � �65:64 �[active][ready]
>> �\_ 1:0:0:28 sdh � � � �8:112 �[active][ready]
>> dm-14_0101 (360060480000290300618533030313031) dm-14 EMC,SYMMETRIX
>> [size=17G][features=0][hwhandler=0]
>> \_ round-robin 0 [prio=2][active]
>> �\_ 0:0:0:24 sdq � � � �65:0 � [active][ready]
>> �\_ 1:0:0:24 sdd � � � �8:48 � [active][ready]
>> dm-8_010D (360060480000290300618533030313044) dm-8 EMC,SYMMETRIX
>> [size=17G][features=0][hwhandler=0]
>> \_ round-robin 0 [prio=2][active]
>> �\_ 0:0:0:30 sdw � � � �65:96 �[active][ready]
>> �\_ 1:0:0:30 sdj � � � �8:144 �[active][ready]
>> dm-15_00FF (360060480000290300618533030304646) dm-15 EMC,SYMMETRIX
>> [size=17G][features=0][hwhandler=0]
>> \_ round-robin 0 [prio=2][active]
>> �\_ 0:0:0:23 sdp � � � �8:240 �[active][ready]
>> �\_ 1:0:0:23 sdc � � � �8:32 � [active][ready]
>> dm-11_0107 (360060480000290300618533030313037) dm-11 EMC,SYMMETRIX
>> [size=17G][features=0][hwhandler=0]
>> \_ round-robin 0 [prio=2][active]
>> �\_ 0:0:0:27 sdt � � � �65:48 �[active][ready]
>> �\_ 1:0:0:27 sdg � � � �8:96 � [active][ready]
>> dm-4_0113 (360060480000290300618533030313133) dm-4 EMC,SYMMETRIX
>> [size=17G][features=0][hwhandler=0]
>> \_ round-robin 0 [prio=2][active]
>> �\_ 0:0:0:33 sdz � � � �65:144 [active][ready]
>> �\_ 1:0:0:33 sdm � � � �8:192 �[active][ready]
>> dm-9_010B (360060480000290300618533030313042) dm-9 EMC,SYMMETRIX
>> [size=17G][features=0][hwhandler=0]
>> \_ round-robin 0 [prio=2][active]
>> �\_ 0:0:0:29 sdv � � � �65:80 �[active][ready]
>> �\_ 1:0:0:29 sdi � � � �8:128 �[active][ready]
>> dm-16_00FD (360060480000290300618533030304644) dm-16 EMC,SYMMETRIX
>> [size=17G][features=0][hwhandler=0]
>> \_ round-robin 0 [prio=2][active]
>> �\_ 0:0:0:22 sdo � � � �8:224 �[active][ready]
>> �\_ 1:0:0:22 sdb � � � �8:16 � [active][ready]
>> dm-12_0105 (360060480000290300618533030313035) dm-12 EMC,SYMMETRIX
>> [size=17G][features=0][hwhandler=0]
>> \_ round-robin 0 [prio=2][active]
>> �\_ 0:0:0:26 sds � � � �65:32 �[active][ready]
>> �\_ 1:0:0:26 sdf � � � �8:80 � [active][ready]
>> dm-5_0111 (360060480000290300618533030313131) dm-5 EMC,SYMMETRIX
>> [size=17G][features=0][hwhandler=0]
>> \_ round-robin 0 [prio=2][active]
>> �\_ 0:0:0:32 sdy � � � �65:128 [active][ready]
>> �\_ 1:0:0:32 sdl � � � �8:176 �[active][ready]
>>
>> Device mapper reports this:
>> # dmsetup ls
>> dm-6_010F � �(253, 6)
>> dm-17_0012 � �(253, 17)
>> dm-13_0103 � �(253, 13)
>> dm-10_0109 � �(253, 10)
>> vg00-app052 � �(253, 3)
>> vg00-xen � �(253, 2)
>> vg00-usr � �(253, 0)
>> vg00-var � �(253, 1)
>> dm-14_0101 � �(253, 14)
>> dm-8_010D � �(253, 8)
>> dm-15_00FF � �(253, 15)
>> dm-11_0107 � �(253, 11)
>> dm-4_0113 � �(253, 4)
>> vg_mds-lvol_mds � �(253, 7)
>> dm-9_010B � �(253, 9)
>> dm-16_00FD � �(253, 16)
>> dm-12_0105 � �(253, 12)
>> dm-5_0111 � �(253, 5)
>>
>>
>> What I do not understand is that surly when I perform a vgscan how will
>> it decide to query only the devices presented from the multipathd, and
>> ignore those presented via the dev/disk/by-id/scsi-nnnnnnnnnn? �Won't it
>> see two vg_mds volumes instead of only those volumes that lie on the
>> multipathed discs, which are the same pshycial discs as the disk/by-id?
>>
>> My plan of action is currently:
>> � � vgchange -a n vg_mds
>> � � vgexport -m /tmp/vg_mds.map mds
>> � � vgexport -f /tmp/vg_mds.pv mds
>> � � vgscan
>> � � vgchange -y a vg_mds
>> � � vgimport vg_mds /*OR instead do it the long way on the next line* �/
>> � � � � vgscan
>> � � � � mkdir /dev/vg_mds
>> � � � � mknod /dev/vg_mds/group c 64 0xNN0000
>> � � � � vgimport -v -s -m /tmp/vg_mds.map /dev/vg_mds
>>
>> I do not see how to tell it to ignore the non-multipathed disc, or has
>> multipathd or LVM have some preference for mutlipath discs over
>> non-multipathed discs, and if so then what is the logic behind the decision?
>>
>> Any help to further my understanding would be gratefully appreciated.
>>
>> Best wishes, S.
>>
>> PS. I am using SLES, but this was the only mailinglist I found for LVM
>> so I subscribed to it. �I think that LVM and multipathd implementations
>> are reasonably similar across Linux distos. Ergo concepts here are
>> applicable to Suse. �The kernel I am using is a xen enabled host (not a
>> guest): 2.6.16.60-0.27-xen #1 SMP.
>>
>>
>
> --
> Simon Loewenthal/Tele2
>
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