Hi list,
I'm having one of those 'I'm stupid' -problems with LVM on CentOS 5.2.
I've been working with traditional partitions until now, but I've
finally been sold on the theoretical benefits of using LVM, but for now
I only have a huge pile of broken filesystems to show for my efforts.
My scenario;
I attach a disk, either over USB or iSCSI.
I create a PV on this device, create a VG using the device, and slice
off a tiny LV for tests.
[root@kasse ~]# dmesg
usb 1-3: new high speed USB device using ehci_hcd and address 7
usb 1-3: configuration #1 chosen from 1 choice
scsi27 : SCSI emulation for USB Mass Storage devices
usb-storage: device found at 7
usb-storage: waiting for device to settle before scanning
Vendor: ST375064 Model: 0A Rev: 3.AA
Type: Direct-Access ANSI SCSI revision: 00
SCSI device sdg: 1465149168 512-byte hdwr sectors (750156 MB)
sdg: Write Protect is off
sdg: Mode Sense: 10 00 00 00
sdg: assuming drive cache: write through
SCSI device sdg: 1465149168 512-byte hdwr sectors (750156 MB)
sdg: Write Protect is off
sdg: Mode Sense: 10 00 00 00
sdg: assuming drive cache: write through
sdg: sdg1
sd 27:0:0:0: Attached scsi disk sdg
sd 27:0:0:0: Attached scsi generic sg6 type 0
usb-storage: device scan complete
[root@kasse ~]# pvcreate /dev/sdg1
Physical volume "/dev/sdg1" successfully created
[root@kasse ~]# vgcreate testgroup /dev/sdg1
Volume group "testgroup" successfully created
[root@kasse ~]# lvcreate -L 200M testgroup -n testLV
Logical volume "testLV" created
At this point, I have /dev/testgroup/testLV, which I can stick a fs on,
mount, store files on, unmount, remount and recover the files from. Just
as I'd expect.
[root@kasse ~]# lvdisplay
--- Logical volume ---
LV Name /dev/testgroup/testLV
VG Name testgroup
LV UUID 3KjDiZ-gTAD-sC9E-sOSA-772o-41Yk-ZKK7cx
LV Write Access read/write
LV Status available
# open 0
LV Size 200.00 MB
Current LE 50
Segments 1
Allocation inherit
Read ahead sectors auto
- currently set to 256
Block device 253:1
I have not explicitly set the vg active, as I understand that it
implicitly will be set active in non-clustered environments like mine.
LVM works as I'd expect it to up until here in any case.
So - with the LV unmounted, I power my USB-device down, and then back up;
[root@kasse ~]# dmesg
usb 1-3: USB disconnect, address 7
usb 1-3: new high speed USB device using ehci_hcd and address 8
usb 1-3: configuration #1 chosen from 1 choice
scsi28 : SCSI emulation for USB Mass Storage devices
usb-storage: device found at 8
usb-storage: waiting for device to settle before scanning
Vendor: ST375064 Model: 0A Rev: 3.AA
Type: Direct-Access ANSI SCSI revision: 00
SCSI device sdi: 1465149168 512-byte hdwr sectors (750156 MB)
sdi: Write Protect is off
sdi: Mode Sense: 10 00 00 00
sdi: assuming drive cache: write through
SCSI device sdi: 1465149168 512-byte hdwr sectors (750156 MB)
sdi: Write Protect is off
sdi: Mode Sense: 10 00 00 00
sdi: assuming drive cache: write through
sdi: sdi1
sd 28:0:0:0: Attached scsi disk sdi
sd 28:0:0:0: Attached scsi generic sg6 type 0
usb-storage: device scan complete
(note that my disk is now sdi, not sdg, and connected on scsi28 and not
scsi27)
If I now try to access the device, all falls appart;
[root@kasse ~]# lvdisplay
/dev/testgroup/testLV: read failed after 0 of 4096 at 209649664:
Input/output error
/dev/testgroup/testLV: read failed after 0 of 4096 at 209707008:
Input/output error
/dev/testgroup/testLV: read failed after 0 of 4096 at 0: Input/output
error
/dev/testgroup/testLV: read failed after 0 of 4096 at 4096:
Input/output error
/dev/testgroup/testLV: read failed after 0 of 4096 at 0: Input/output
error
--- Logical volume ---
LV Name /dev/testgroup/testLV
VG Name testgroup
LV UUID 3KjDiZ-gTAD-sC9E-sOSA-772o-41Yk-ZKK7cx
LV Write Access read/write
LV Status available
# open 0
LV Size 200.00 MB
Current LE 50
Segments 1
Allocation inherit
Read ahead sectors auto
- currently set to 256
Block device 253:1
Trying to mount or otherwise access the LV also shows the problems;
scsi 27:0:0:0: rejecting I/O to dead device
scsi 27:0:0:0: rejecting I/O to dead device
scsi 27:0:0:0: rejecting I/O to dead device
scsi 27:0:0:0: rejecting I/O to dead device
scsi 27:0:0:0: rejecting I/O to dead device
scsi 27:0:0:0: rejecting I/O to dead device
printk: 25 messages suppressed.
Buffer I/O error on device dm-1, logical block 30
Buffer I/O error on device dm-1, logical block 31
scsi 27:0:0:0: rejecting I/O to dead device
Buffer I/O error on device dm-1, logical block 0
Buffer I/O error on device dm-1, logical block 1
Buffer I/O error on device dm-1, logical block 2
Buffer I/O error on device dm-1, logical block 3
Buffer I/O error on device dm-1, logical block 4
Buffer I/O error on device dm-1, logical block 5
Buffer I/O error on device dm-1, logical block 6
Buffer I/O error on device dm-1, logical block 7
scsi 27:0:0:0: rejecting I/O to dead device
scsi 27:0:0:0: rejecting I/O to dead device
scsi 27:0:0:0: rejecting I/O to dead device
scsi 27:0:0:0: rejecting I/O to dead device
hfs: unable to find HFS+ superblock
So - LVM seems to believe my LV is still attached to scsi27, while it
now actually sits on scsi28.
What am I missing here?
How do I get LVM to use a persistent device instead of a transient path?
Yours,
-S
--
Simen Thoresen, Dolphin ICS
Systems Administration and Wulfkit Support
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