HP-UX System Administrator's Guide: Logical Volume Management HP-UX 11i v3 (B3921-90053 September 2011) Transform used: ESS version 2.2
# dd if=/dev/rdsk/c0t5d0 of=/dev/null bs=1024k count=64
64+0 records in
64+0 records out
NOTE: If the dd command hangs or takes a long time, Ctrl+C stops the read on the disk.
To run dd on the background, add & at the end of the command.
The following command shows an unsuccessful read of the whole disk:
# dd if=/dev/rdsk/c1t3d0 of=/dev/null bs=1024k
dd read error: I/O error
0+0 records in 0+0 records out
4. If the physical volume is attached but cannot be refreshed via an lvsync, it is likely there is
a media problem at a specific location. Reading only the extents associated with the LE can
help isolate the problem. Remember the stale extent might not have the problem. The lvsync
command starts refreshing extents at LE zero and stops if it encounters an error. Therefore,
find the first LE in any logical volume that is stale and test this one. For example:
a. Find the first stale LE:
# lvdisplay –v /dev/vg01/lvol3 | more
LV Status available/stale
.
.
.
--- Logical extents ---
LE PV1 PE1 Status 1 PV2 PE2 Status 2
0000 /dev/dsk/c0t3d0 0000 current /dev/dsk/c1t3d0 0100 current
0001 /dev/dsk/c0t3d0 0001 current /dev/dsk/c1t3d0 0101 current
0002 /dev/dsk/c0t3d0 0002 current /dev/dsk/c1t3d0 0102 stale
0003 /dev/dsk/c0t3d0 0003 current /dev/dsk/c1t3d0 0103 stale
In this case, LE number 2 is stale.
b. Get the extent size for the VG:
# vgdisplay /dev/vg01 | grep –I “PE Size”
PE size (Mbytes) 32
c. Find the start of PE zero on each disk:
For a version 1.0 VG, enter:
xd -j 0x2048 -t uI -N 4 /dev/dsk/c0t3d0
For a version 2.x VG, enter:
xd -j 0x21a4 -t uI -N 4 /dev/dsk/c0t3d0
In this example, this is a version 1.0 VG.
# xd -j 0x2048 -t uI -N 4 /dev/dsk/c0t3d0
0000000 1024
0000004
# xd -j 0x2048 -t uI -N 4 /dev/dsk/c1t3d0
0000000 1024
0000004
d. Calculate the location of the physical extent for each PV. Multiply the PE number by the
PE size and then by 1024 to convert to Kb:
2 * 32 * 1024 = 65536
Add the offset to PE zero:
65536 + 1024 = 66560
e. Enter the following dd commands:
# dd bs=1k skip=66560 count=32768 if=/dev/rdsk/c0t3d0 of=/dev/null
# dd bs=1k skip=66560 count=32768 if=/dev/rdsk/c1t3d0 of=/dev/null
Disk Troubleshooting and Recovery Procedures 121