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Red Hat Enterprise Linux 6 -Missing LVM Disk

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Environment


Some system with an RHEL 6.4 installation and access to different LUNs in the SAN

Questions/Symptoms


After a failure in the SAN infrastructure the LVM commands reports a
missing disk even if all SAN problems are solved and all LUNs are
accessible. A reboot did not solve the problem.

Cause



All disks are visible in the LVM command outputs but one of them is
not active

#> pvscan -v | grep vgdata
PV /dev/mapper/mpatha VG vgdata lvm2 [639.98 GiB / 40.01 GiB free]
PV /dev/mapper/mpathb VG vgdata lvm2 [639.98 GiB / 4.00 MiB free]

#> vgdisplay -v vgdata
...
--- Volume group ---
VG Name vgdata
...
Max PV 0
Cur PV 2
Act PV 1 <<<<=========
...
--- Physical volumes ---
PV Name /dev/mapper/mpatha
PV UUID 9MPeL7-42rB-05CB-Fgc5-HLz8-Zi2d-MJ2bwA
PV Status allocatable
Total PE / Free PE 163836 / 10243

PV Name /dev/mapper/mpathb
PV UUID RjRo4D-iH4C-hPgR-5CJ6-Usrf-Cfwp-JsaZfb
PV Status allocatable
Total PE / Free PE 163836 / 1


Only one disk is shown as active and the backup file of the volume group configuration /etc/lvm/backup/vgdata shows that one of the disk is marked as "MISSING", there is a segment

pv0 {
id = "9MPeL7-42rB-05CB-Fgc5-HLz8-Zi2d-MJ2bwA"
device = "/dev/mapper/mpatha" # Hint only
status = ["ALLOCATABLE"]
flags = ["MISSING"]
dev_size = 1342177280 # 640 Gigabytes
pe_start = 32768
pe_count = 163836 # 639.984 Gigabytes
}


The "MISSING" flag blocks the normal work !

Answer/Solution



1) Check which device file is currently used for "pv0"

pvs -a -v |grep 9MPeL7-42rB-05CB-Fgc5-HLz8-Zi2d-MJ2bwA

2) Run the command (replace mpatha if step 1 shows an other device)

vgextend --restoremissing vgdata /dev/mapper/mpatha


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