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
GSM: +31 6 2000 5427
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