Discussion:
[linux-lvm] Raid 10 - recovery after a disk failure
Pavlik Kirilov
2016-01-31 23:00:39 UTC
Permalink
Hi,

I am encountering strange behaviour when trying to recover a Raid 10 LV, created with the following command:


lvcreate --type raid10 -L3G -i 2 -I 256 -n lv_r10 vg_data /dev/vdb1:1-500 /dev/vdc1:1-500 /dev/vdd1:1-500 /dev/vde1:1-500

As it can be seen, I have 4 PVs and give the first 500 PE of each of them for the raid 10 logical volume. I am able to see the following PE layout:

lvs -o seg_pe_ranges,lv_name,stripes -a

PE Ranges LV #Str
lv_r10_rimage_0:0-767 lv_r10_rimage_1:0-767 lv_r10_rimage_2:0-767 lv_r10_rimage_3:0-767 lv_r10 4
/dev/vdb1:2-385 [lv_r10_rimage_0] 1
/dev/vdc1:2-385 [lv_r10_rimage_1] 1
/dev/vdd1:2-385 [lv_r10_rimage_2] 1
/dev/vde1:2-385 [lv_r10_rimage_3] 1
/dev/vdb1:1-1 [lv_r10_rmeta_0] 1
/dev/vdc1:1-1 [lv_r10_rmeta_1] 1
/dev/vdd1:1-1 [lv_r10_rmeta_2] 1
/dev/vde1:1-1 [lv_r10_rmeta_3] 1


So far everything is OK and the number of PE is automatically reduced to 385 per PV to have the size equal to 3 Gigabytes.

The problem comes when I shut down the system, replace one disk (vdc), boot again and try to recover the array. Here are the commands I execute:
pvs
Couldn't find device with uuid 2hU2pD-xNDa-yi1J-OkkP-NjGq-hIxo-Q5AgQC.
PV VG Fmt Attr PSize PFree
/dev/vdb1 vg_data lvm2 a-- 8.00g 6.49g
/dev/vdd1 vg_data lvm2 a-- 8.00g 6.49g
/dev/vde1 vg_data lvm2 a-- 8.00g 6.49g
unknown device vg_data lvm2 a-m 8.00g 6.49g

pvcreate /dev/vdc1
Physical volume "/dev/vdc1" successfully created

vgextend vg_data /dev/vdc1
Couldn't find device with uuid 2hU2pD-xNDa-yi1J-OkkP-NjGq-hIxo-Q5AgQC
Volume group "vg_data" successfully extended

lvs -o seg_pe_ranges,lv_name,stripes -a
Couldn't find device with uuid 2hU2pD-xNDa-yi1J-OkkP-NjGq-hIxo-Q5AgQC.
PE Ranges LV #Str
lv_r10_rimage_0:0-767 lv_r10_rimage_1:0-767 lv_r10_rimage_2:0-767 lv_r10_rimage_3:0-767 lv_r10 4
/dev/vdb1:2-385 [lv_r10_rimage_0] 1
unknown device:2-385 [lv_r10_rimage_1] 1
/dev/vdd1:2-385 [lv_r10_rimage_2] 1
/dev/vde1:2-385 [lv_r10_rimage_3] 1
/dev/vdb1:1-1 [lv_r10_rmeta_0] 1
unknown device:1-1 [lv_r10_rmeta_1] 1
/dev/vdd1:1-1 [lv_r10_rmeta_2] 1
/dev/vde1:1-1 [lv_r10_rmeta_3] 1

lvchange -ay --partial /dev/vg_data/lv_r10
PARTIAL MODE. Incomplete logical volumes will be processed.
Couldn't find device with uuid 2hU2pD-xNDa-yi1J-OkkP-NjGq-hIxo-Q5AgQC

lvconvert --repair vg_data/lv_r10 /dev/vdc1:1-385
Attempt to replace failed RAID images (requires full device resync)? [y/n]: y
Insufficient free space: 770 extents needed, but only 345 available
Failed to allocate replacement images for vg_data/lv_r10

lvconvert --repair vg_data/lv_r10
Attempt to replace failed RAID images (requires full device resync)? [y/n]: y
Faulty devices in vg_data/lv_r10 successfully replaced.

lvs -o seg_pe_ranges,lv_name,stripes -a
Couldn't find device with uuid
2hU2pD-xNDa-yi1J-OkkP-NjGq-hIxo-Q5AgQC.

PE Ranges LV #Str
lv_r10_rimage_0:0-767 lv_r10_rimage_1:0-767 lv_r10_rimage_2:0-767 lv_r10_rimage_3:0-767 lv_r10 4
/dev/vdb1:2-385 [lv_r10_rimage_0] 1
/dev/vdc1:1-768 [lv_r10_rimage_1] 1
/dev/vdd1:2-385 [lv_r10_rimage_2] 1
/dev/vde1:2-385 [lv_r10_rimage_3] 1
/dev/vdb1:1-1 [lv_r10_rmeta_0] 1
/dev/vdc1:0-0 [lv_r10_rmeta_1] 1
/dev/vdd1:1-1 [lv_r10_rmeta_2] 1
/dev/vde1:1-1 [lv_r10_rmeta_3] 1

The array was recovered, but it is definitely not what I expected, because on /dev/vdc1 now 768 PEs are used instead of 385, like on the other PVs. In this case I had some extra free space on /dev/vdc1, but what if I did not? Please, suggest what should be done.

Linux ubuntu1 3.13.0-32-generic, x86_64
LVM version: 2.02.98(2) (2012-10-15)
Library version: 1.02.77 (2012-10-15)
Driver version: 4.27.0

Pavlik Petrov
emmanuel segura
2016-01-31 23:23:07 UTC
Permalink
You used pvcreate without the required options to create the physical
in your new disk and set the old uuid


example:

pvcreate --uuid "FmGRh3-zhok-iVI8-7qTD-S5BI-MAEN-NYM5Sk" --restorefile
/etc/lvm/archive/VG_00050.vg /dev/sdh1

https://www.centos.org/docs/5/html/Cluster_Logical_Volume_Manager/mdatarecover.html
Post by Pavlik Kirilov
Hi,
lvcreate --type raid10 -L3G -i 2 -I 256 -n lv_r10 vg_data /dev/vdb1:1-500 /dev/vdc1:1-500 /dev/vdd1:1-500 /dev/vde1:1-500
lvs -o seg_pe_ranges,lv_name,stripes -a
PE Ranges LV #Str
lv_r10_rimage_0:0-767 lv_r10_rimage_1:0-767 lv_r10_rimage_2:0-767 lv_r10_rimage_3:0-767 lv_r10 4
/dev/vdb1:2-385 [lv_r10_rimage_0] 1
/dev/vdc1:2-385 [lv_r10_rimage_1] 1
/dev/vdd1:2-385 [lv_r10_rimage_2] 1
/dev/vde1:2-385 [lv_r10_rimage_3] 1
/dev/vdb1:1-1 [lv_r10_rmeta_0] 1
/dev/vdc1:1-1 [lv_r10_rmeta_1] 1
/dev/vdd1:1-1 [lv_r10_rmeta_2] 1
/dev/vde1:1-1 [lv_r10_rmeta_3] 1
So far everything is OK and the number of PE is automatically reduced to 385 per PV to have the size equal to 3 Gigabytes.
pvs
Couldn't find device with uuid 2hU2pD-xNDa-yi1J-OkkP-NjGq-hIxo-Q5AgQC.
PV VG Fmt Attr PSize PFree
/dev/vdb1 vg_data lvm2 a-- 8.00g 6.49g
/dev/vdd1 vg_data lvm2 a-- 8.00g 6.49g
/dev/vde1 vg_data lvm2 a-- 8.00g 6.49g
unknown device vg_data lvm2 a-m 8.00g 6.49g
pvcreate /dev/vdc1
Physical volume "/dev/vdc1" successfully created
vgextend vg_data /dev/vdc1
Couldn't find device with uuid 2hU2pD-xNDa-yi1J-OkkP-NjGq-hIxo-Q5AgQC
Volume group "vg_data" successfully extended
lvs -o seg_pe_ranges,lv_name,stripes -a
Couldn't find device with uuid 2hU2pD-xNDa-yi1J-OkkP-NjGq-hIxo-Q5AgQC.
PE Ranges LV #Str
lv_r10_rimage_0:0-767 lv_r10_rimage_1:0-767 lv_r10_rimage_2:0-767 lv_r10_rimage_3:0-767 lv_r10 4
/dev/vdb1:2-385 [lv_r10_rimage_0] 1
unknown device:2-385 [lv_r10_rimage_1] 1
/dev/vdd1:2-385 [lv_r10_rimage_2] 1
/dev/vde1:2-385 [lv_r10_rimage_3] 1
/dev/vdb1:1-1 [lv_r10_rmeta_0] 1
unknown device:1-1 [lv_r10_rmeta_1] 1
/dev/vdd1:1-1 [lv_r10_rmeta_2] 1
/dev/vde1:1-1 [lv_r10_rmeta_3] 1
lvchange -ay --partial /dev/vg_data/lv_r10
PARTIAL MODE. Incomplete logical volumes will be processed.
Couldn't find device with uuid 2hU2pD-xNDa-yi1J-OkkP-NjGq-hIxo-Q5AgQC
lvconvert --repair vg_data/lv_r10 /dev/vdc1:1-385
Attempt to replace failed RAID images (requires full device resync)? [y/n]: y
Insufficient free space: 770 extents needed, but only 345 available
Failed to allocate replacement images for vg_data/lv_r10
lvconvert --repair vg_data/lv_r10
Attempt to replace failed RAID images (requires full device resync)? [y/n]: y
Faulty devices in vg_data/lv_r10 successfully replaced.
lvs -o seg_pe_ranges,lv_name,stripes -a
Couldn't find device with uuid
2hU2pD-xNDa-yi1J-OkkP-NjGq-hIxo-Q5AgQC.
PE Ranges LV #Str
lv_r10_rimage_0:0-767 lv_r10_rimage_1:0-767 lv_r10_rimage_2:0-767 lv_r10_rimage_3:0-767 lv_r10 4
/dev/vdb1:2-385 [lv_r10_rimage_0] 1
/dev/vdc1:1-768 [lv_r10_rimage_1] 1
/dev/vdd1:2-385 [lv_r10_rimage_2] 1
/dev/vde1:2-385 [lv_r10_rimage_3] 1
/dev/vdb1:1-1 [lv_r10_rmeta_0] 1
/dev/vdc1:0-0 [lv_r10_rmeta_1] 1
/dev/vdd1:1-1 [lv_r10_rmeta_2] 1
/dev/vde1:1-1 [lv_r10_rmeta_3] 1
The array was recovered, but it is definitely not what I expected, because on /dev/vdc1 now 768 PEs are used instead of 385, like on the other PVs. In this case I had some extra free space on /dev/vdc1, but what if I did not? Please, suggest what should be done.
Linux ubuntu1 3.13.0-32-generic, x86_64
LVM version: 2.02.98(2) (2012-10-15)
Library version: 1.02.77 (2012-10-15)
Driver version: 4.27.0
Pavlik Petrov
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linux-lvm mailing list
https://www.redhat.com/mailman/listinfo/linux-lvm
read the LVM HOW-TO at http://tldp.org/HOWTO/LVM-HOWTO/
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^`~'^
Pavlik Kirilov
2016-02-01 17:06:42 UTC
Permalink
The method for restoring raid 10, which I posted in my previous email, works very well for raid 5 on 4 PVs. I tried many times the "--uuid" method from the link you sent me and I always end up with destroyed data. Here comes the output of the tests I performed:

## Ubuntu VM with 4 new disks (qcow files) vda,vdb,vdc,vdd, one physical partition per disk.

vgcreate vg_data /dev/vda1 /dev/vdb1 /dev/vdc1 /dev/vdd1
Volume group "vg_data" successfully created

lvcreate --type raid10 -L3g -i 2 -I 256 -n lv_r10 vg_data /dev/vda1:1-900 /dev/vdb1:1-900 /dev/vdc1:1-900 /dev/vdd1:1-900
Logical volume "lv_r10" created

mkfs.ext4 /dev/vg_data/lv_r10

mount /dev/vg_data/lv_r10 /mnt/r10/

mount | grep vg_data
/dev/mapper/vg_data-lv_r10 on /mnt/r10 type ext4 (rw)

echo "some data" > /mnt/r10/testr10.txt

dmesg -T | tail -n 70

------------------

[ 3822.367551] EXT4-fs (dm-8): mounted filesystem with ordered data mode. Opts: (null)
[ 3851.317428] md: mdX: resync done.
[ 3851.440927] RAID10 conf printout:
[ 3851.440935] --- wd:4 rd:4
[ 3851.440941] disk 0, wo:0, o:1, dev:dm-1
[ 3851.440945] disk 1, wo:0, o:1, dev:dm-3
[ 3851.440949] disk 2, wo:0, o:1, dev:dm-5
[ 3851.440953] disk 3, wo:0, o:1, dev:dm-7


lvs -a -o +devices
LV VG Attr LSize Pool Origin Data% Move Log Copy% Convert Devices
lv_r10 vg_data rwi-aor-- 3.00g 100.00 lv_r10_rimage_0(0),lv_r10_rimage_1(0),lv_r10_rimage_2(0),lv_r10_rimage_3(0)
[lv_r10_rimage_0] vg_data iwi-aor-- 1.50g /dev/vda1(2)
[lv_r10_rimage_1] vg_data iwi-aor-- 1.50g /dev/vdb1(2)
[lv_r10_rimage_2] vg_data iwi-aor-- 1.50g /dev/vdc1(2)
[lv_r10_rimage_3] vg_data iwi-aor-- 1.50g /dev/vdd1(2)
[lv_r10_rmeta_0] vg_data ewi-aor-- 4.00m /dev/vda1(1)
[lv_r10_rmeta_1] vg_data ewi-aor-- 4.00m /dev/vdb1(1)
[lv_r10_rmeta_2] vg_data ewi-aor-- 4.00m /dev/vdc1(1)
[lv_r10_rmeta_3] vg_data ewi-aor-- 4.00m /dev/vdd1(1)
###

### Shutting down, replacing vdb with a new disk, starting the system ###

###
lvs -a -o +devices
Couldn't find device with uuid GjkgzF-18Ls-321G-SaDW-4vp0-d04y-Gd4xRp.
LV VG Attr LSize Pool Origin Data% Move Log Copy% Convert Devices
lv_r10 vg_data rwi---r-p 3.00g lv_r10_rimage_0(0),lv_r10_rimage_1(0),lv_r10_rimage_2(0),lv_r10_rimage_3(0)
[lv_r10_rimage_0] vg_data Iwi---r-- 1.50g /dev/vda1(2)
[lv_r10_rimage_1] vg_data Iwi---r-p 1.50g unknown device(2)
[lv_r10_rimage_2] vg_data Iwi---r-- 1.50g /dev/vdc1(2)
[lv_r10_rimage_3] vg_data Iwi---r-- 1.50g /dev/vdd1(2)
[lv_r10_rmeta_0] vg_data ewi---r-- 4.00m /dev/vda1(1)
[lv_r10_rmeta_1] vg_data ewi---r-p 4.00m unknown device(1)
[lv_r10_rmeta_2] vg_data ewi---r-- 4.00m /dev/vdc1(1)
[lv_r10_rmeta_3] vg_data ewi---r-- 4.00m /dev/vdd1(1)

grep description /etc/lvm/backup/vg_data
description = "Created *after* executing 'lvcreate --type raid10 -L3g -i 2 -I 256 -n lv_r10 vg_data /dev/vda1:1-900 /dev/vdb1:1-900 /dev/vdc1:1-900 /dev/vdd1:1-900'"

pvcreate --uuid GjkgzF-18Ls-321G-SaDW-4vp0-d04y-Gd4xRp --restorefile /etc/lvm/backup/vg_data /dev/vdb1
Couldn't find device with uuid GjkgzF-18Ls-321G-SaDW-4vp0-d04y-Gd4xRp.
Physical volume "/dev/vdb1" successfully created

vgcfgrestore vg_data
Restored volume group vg_data

lvs -a -o +devices
LV VG Attr LSize Pool Origin Data% Move Log Copy% Convert Devices
lv_r10 vg_data rwi-d-r-- 3.00g 0.00 lv_r10_rimage_0(0),lv_r10_rimage_1(0),lv_r10_rimage_2(0),lv_r10_rimage_3(0)
[lv_r10_rimage_0] vg_data iwi-a-r-- 1.50g /dev/vda1(2)
[lv_r10_rimage_1] vg_data iwi-a-r-- 1.50g /dev/vdb1(2)
[lv_r10_rimage_2] vg_data iwi-a-r-- 1.50g /dev/vdc1(2)
[lv_r10_rimage_3] vg_data iwi-a-r-- 1.50g /dev/vdd1(2)
[lv_r10_rmeta_0] vg_data ewi-a-r-- 4.00m /dev/vda1(1)
[lv_r10_rmeta_1] vg_data ewi-a-r-- 4.00m /dev/vdb1(1)
[lv_r10_rmeta_2] vg_data ewi-a-r-- 4.00m /dev/vdc1(1)
[lv_r10_rmeta_3] vg_data ewi-a-r-- 4.00m /dev/vdd1(1)

lvchange --resync vg_data/lv_r10
Do you really want to deactivate logical volume lv_r10 to resync it? [y/n]: y

lvs -a -o +devices
LV VG Attr LSize Pool Origin Data% Move Log Copy% Convert Devices
lv_r10 vg_data rwi-a-r-- 3.00g 100.00
---------

dmesg | tail
------------
[ 708.691297] md: mdX: resync done.
[ 708.765376] RAID10 conf printout:
[ 708.765379] --- wd:4 rd:4
[ 708.765381] disk 0, wo:0, o:1, dev:dm-1
[ 708.765382] disk 1, wo:0, o:1, dev:dm-3
[ 708.765383] disk 2, wo:0, o:1, dev:dm-5
[ 708.765384] disk 3, wo:0, o:1, dev:dm-7

mount /dev/vg_data/lv_r10 /mnt/r10/
cat /mnt/r10/testr10.txt
some data

### Suppose now that vda must be replaced too.
### Shutting down again, replacing vda with a new disk, starting the system ###

lvs -a -o +devices
Couldn't find device with uuid KGf6QK-1LrJ-JDaA-bJJY-pmLb-l9eV-LEXgT2.
LV VG Attr LSize Pool Origin Data% Move Log Copy% Convert Devices
lv_r10 vg_data rwi---r-p 3.00g lv_r10_rimage_0(0),lv_r10_rimage_1(0),lv_r10_rimage_2(0),lv_r10_rimage_3(0)
[lv_r10_rimage_0] vg_data Iwi---r-p 1.50g unknown device(2)
[lv_r10_rimage_1] vg_data Iwi---r-- 1.50g /dev/vdb1(2)
[lv_r10_rimage_2] vg_data Iwi---r-- 1.50g /dev/vdc1(2)
[lv_r10_rimage_3] vg_data Iwi---r-- 1.50g /dev/vdd1(2)
[lv_r10_rmeta_0] vg_data ewi---r-p 4.00m unknown device(1)
[lv_r10_rmeta_1] vg_data ewi---r-- 4.00m /dev/vdb1(1)
[lv_r10_rmeta_2] vg_data ewi---r-- 4.00m /dev/vdc1(1)
[lv_r10_rmeta_3] vg_data ewi---r-- 4.00m /dev/vdd1(1)


grep description /etc/lvm/backup/vg_data
description = "Created *after* executing 'vgscan'"
pvcreate --uuid KGf6QK-1LrJ-JDaA-bJJY-pmLb-l9eV-LEXgT2 --restorefile /etc/lvm/backup/vg_data /dev/vda1
Couldn't find device with uuid KGf6QK-1LrJ-JDaA-bJJY-pmLb-l9eV-LEXgT2.
Physical volume "/dev/vda1" successfully created

vgcfgrestore vg_data
Restored volume group vg_data

lvchange --resync vg_data/lv_r10
Do you really want to deactivate logical volume lv_r10 to resync it? [y/n]: y

lvs -a -o +devices
LV VG Attr LSize Pool Origin Data% Move Log Copy% Convert Devices
lv_r10 vg_data rwi-a-r-- 3.00g 100.00 lv_r10_rimage_0(0),lv_r10_rimage_1(0),lv_r10_rimage_2(0),lv_r10_rimage_3(0)
[lv_r10_rimage_0] vg_data iwi-aor-- 1.50g /dev/vda1(2)
[lv_r10_rimage_1] vg_data iwi-aor-- 1.50g /dev/vdb1(2)
[lv_r10_rimage_2] vg_data iwi-aor-- 1.50g /dev/vdc1(2)
[lv_r10_rimage_3] vg_data iwi-aor-- 1.50g /dev/vdd1(2)
[lv_r10_rmeta_0] vg_data ewi-aor-- 4.00m /dev/vda1(1)
[lv_r10_rmeta_1] vg_data ewi-aor-- 4.00m /dev/vdb1(1)
[lv_r10_rmeta_2] vg_data ewi-aor-- 4.00m /dev/vdc1(1)
[lv_r10_rmeta_3] vg_data ewi-aor-- 4.00m /dev/vdd1(1)

mount -t ext4 /dev/vg_data/lv_r10 /mnt/r10/
mount: wrong fs type, bad option, bad superblock on /dev/mapper/vg_data-lv_r10,
missing codepage or helper program, or other error
In some cases useful info is found in syslog - try
dmesg | tail or so

dmesg | tail
-------------
[ 715.361985] EXT4-fs (dm-8): VFS: Can't find ext4 filesystem
[ 715.362248] EXT4-fs (dm-8): VFS: Can't find ext4 filesystem
[ 715.362548] EXT4-fs (dm-8): VFS: Can't find ext4 filesystem
[ 715.362846] FAT-fs (dm-8): bogus number of reserved sectors
[ 715.362933] FAT-fs (dm-8): Can't find a valid FAT filesystem
[ 729.843473] EXT4-fs (dm-8): VFS: Can't find ext4 filesystem

As you can see, after more then one disk failure and raid repair , I lost the file system on the raid 10 volume. Please, suggest what I am doing wrong.Thanks.

Pavlik
emmanuel segura
2016-02-01 18:22:00 UTC
Permalink
please can you retry using:

--[raid]syncaction {check|repair}
This argument is used to initiate various RAID
synchronization operations. The check and repair options provide a
way to check the integrity of a RAID log‐
ical volume (often referred to as "scrubbing").
These options cause the RAID logical volume to read all of the data
and parity blocks in the array and
check for any discrepancies (e.g. mismatches between
mirrors or incorrect parity values). If check is used, the
discrepancies will be counted but not
repaired. If repair is used, the discrepancies will
be corrected as they are encountered. The 'lvs' command can be used
to show the number of discrepan‐
cies found or repaired.

maybe --resync is for mirror and you are using raid

--resync
Forces the complete resynchronization of a mirror. In
normal circumstances you should not need this option because
synchronization happens automatically.
Data is read from the primary mirror device and copied
to the others, so this can take a considerable amount of time - and
during this time you are without
a complete redundant copy of your data.
Post by Pavlik Kirilov
## Ubuntu VM with 4 new disks (qcow files) vda,vdb,vdc,vdd, one physical partition per disk.
vgcreate vg_data /dev/vda1 /dev/vdb1 /dev/vdc1 /dev/vdd1
Volume group "vg_data" successfully created
lvcreate --type raid10 -L3g -i 2 -I 256 -n lv_r10 vg_data /dev/vda1:1-900 /dev/vdb1:1-900 /dev/vdc1:1-900 /dev/vdd1:1-900
Logical volume "lv_r10" created
mkfs.ext4 /dev/vg_data/lv_r10
mount /dev/vg_data/lv_r10 /mnt/r10/
mount | grep vg_data
/dev/mapper/vg_data-lv_r10 on /mnt/r10 type ext4 (rw)
echo "some data" > /mnt/r10/testr10.txt
dmesg -T | tail -n 70
------------------
[ 3822.367551] EXT4-fs (dm-8): mounted filesystem with ordered data mode. Opts: (null)
[ 3851.317428] md: mdX: resync done.
[ 3851.440935] --- wd:4 rd:4
[ 3851.440941] disk 0, wo:0, o:1, dev:dm-1
[ 3851.440945] disk 1, wo:0, o:1, dev:dm-3
[ 3851.440949] disk 2, wo:0, o:1, dev:dm-5
[ 3851.440953] disk 3, wo:0, o:1, dev:dm-7
lvs -a -o +devices
LV VG Attr LSize Pool Origin Data% Move Log Copy% Convert Devices
lv_r10 vg_data rwi-aor-- 3.00g 100.00 lv_r10_rimage_0(0),lv_r10_rimage_1(0),lv_r10_rimage_2(0),lv_r10_rimage_3(0)
[lv_r10_rimage_0] vg_data iwi-aor-- 1.50g /dev/vda1(2)
[lv_r10_rimage_1] vg_data iwi-aor-- 1.50g /dev/vdb1(2)
[lv_r10_rimage_2] vg_data iwi-aor-- 1.50g /dev/vdc1(2)
[lv_r10_rimage_3] vg_data iwi-aor-- 1.50g /dev/vdd1(2)
[lv_r10_rmeta_0] vg_data ewi-aor-- 4.00m /dev/vda1(1)
[lv_r10_rmeta_1] vg_data ewi-aor-- 4.00m /dev/vdb1(1)
[lv_r10_rmeta_2] vg_data ewi-aor-- 4.00m /dev/vdc1(1)
[lv_r10_rmeta_3] vg_data ewi-aor-- 4.00m /dev/vdd1(1)
###
### Shutting down, replacing vdb with a new disk, starting the system ###
###
lvs -a -o +devices
Couldn't find device with uuid GjkgzF-18Ls-321G-SaDW-4vp0-d04y-Gd4xRp.
LV VG Attr LSize Pool Origin Data% Move Log Copy% Convert Devices
lv_r10 vg_data rwi---r-p 3.00g lv_r10_rimage_0(0),lv_r10_rimage_1(0),lv_r10_rimage_2(0),lv_r10_rimage_3(0)
[lv_r10_rimage_0] vg_data Iwi---r-- 1.50g /dev/vda1(2)
[lv_r10_rimage_1] vg_data Iwi---r-p 1.50g unknown device(2)
[lv_r10_rimage_2] vg_data Iwi---r-- 1.50g /dev/vdc1(2)
[lv_r10_rimage_3] vg_data Iwi---r-- 1.50g /dev/vdd1(2)
[lv_r10_rmeta_0] vg_data ewi---r-- 4.00m /dev/vda1(1)
[lv_r10_rmeta_1] vg_data ewi---r-p 4.00m unknown device(1)
[lv_r10_rmeta_2] vg_data ewi---r-- 4.00m /dev/vdc1(1)
[lv_r10_rmeta_3] vg_data ewi---r-- 4.00m /dev/vdd1(1)
grep description /etc/lvm/backup/vg_data
description = "Created *after* executing 'lvcreate --type raid10 -L3g -i 2 -I 256 -n lv_r10 vg_data /dev/vda1:1-900 /dev/vdb1:1-900 /dev/vdc1:1-900 /dev/vdd1:1-900'"
pvcreate --uuid GjkgzF-18Ls-321G-SaDW-4vp0-d04y-Gd4xRp --restorefile /etc/lvm/backup/vg_data /dev/vdb1
Couldn't find device with uuid GjkgzF-18Ls-321G-SaDW-4vp0-d04y-Gd4xRp.
Physical volume "/dev/vdb1" successfully created
vgcfgrestore vg_data
Restored volume group vg_data
lvs -a -o +devices
LV VG Attr LSize Pool Origin Data% Move Log Copy% Convert Devices
lv_r10 vg_data rwi-d-r-- 3.00g 0.00 lv_r10_rimage_0(0),lv_r10_rimage_1(0),lv_r10_rimage_2(0),lv_r10_rimage_3(0)
[lv_r10_rimage_0] vg_data iwi-a-r-- 1.50g /dev/vda1(2)
[lv_r10_rimage_1] vg_data iwi-a-r-- 1.50g /dev/vdb1(2)
[lv_r10_rimage_2] vg_data iwi-a-r-- 1.50g /dev/vdc1(2)
[lv_r10_rimage_3] vg_data iwi-a-r-- 1.50g /dev/vdd1(2)
[lv_r10_rmeta_0] vg_data ewi-a-r-- 4.00m /dev/vda1(1)
[lv_r10_rmeta_1] vg_data ewi-a-r-- 4.00m /dev/vdb1(1)
[lv_r10_rmeta_2] vg_data ewi-a-r-- 4.00m /dev/vdc1(1)
[lv_r10_rmeta_3] vg_data ewi-a-r-- 4.00m /dev/vdd1(1)
lvchange --resync vg_data/lv_r10
Do you really want to deactivate logical volume lv_r10 to resync it? [y/n]: y
lvs -a -o +devices
LV VG Attr LSize Pool Origin Data% Move Log Copy% Convert Devices
lv_r10 vg_data rwi-a-r-- 3.00g 100.00
---------
dmesg | tail
------------
[ 708.691297] md: mdX: resync done.
[ 708.765379] --- wd:4 rd:4
[ 708.765381] disk 0, wo:0, o:1, dev:dm-1
[ 708.765382] disk 1, wo:0, o:1, dev:dm-3
[ 708.765383] disk 2, wo:0, o:1, dev:dm-5
[ 708.765384] disk 3, wo:0, o:1, dev:dm-7
mount /dev/vg_data/lv_r10 /mnt/r10/
cat /mnt/r10/testr10.txt
some data
### Suppose now that vda must be replaced too.
### Shutting down again, replacing vda with a new disk, starting the system ###
lvs -a -o +devices
Couldn't find device with uuid KGf6QK-1LrJ-JDaA-bJJY-pmLb-l9eV-LEXgT2.
LV VG Attr LSize Pool Origin Data% Move Log Copy% Convert Devices
lv_r10 vg_data rwi---r-p 3.00g lv_r10_rimage_0(0),lv_r10_rimage_1(0),lv_r10_rimage_2(0),lv_r10_rimage_3(0)
[lv_r10_rimage_0] vg_data Iwi---r-p 1.50g unknown device(2)
[lv_r10_rimage_1] vg_data Iwi---r-- 1.50g /dev/vdb1(2)
[lv_r10_rimage_2] vg_data Iwi---r-- 1.50g /dev/vdc1(2)
[lv_r10_rimage_3] vg_data Iwi---r-- 1.50g /dev/vdd1(2)
[lv_r10_rmeta_0] vg_data ewi---r-p 4.00m unknown device(1)
[lv_r10_rmeta_1] vg_data ewi---r-- 4.00m /dev/vdb1(1)
[lv_r10_rmeta_2] vg_data ewi---r-- 4.00m /dev/vdc1(1)
[lv_r10_rmeta_3] vg_data ewi---r-- 4.00m /dev/vdd1(1)
grep description /etc/lvm/backup/vg_data
description = "Created *after* executing 'vgscan'"
pvcreate --uuid KGf6QK-1LrJ-JDaA-bJJY-pmLb-l9eV-LEXgT2 --restorefile /etc/lvm/backup/vg_data /dev/vda1
Couldn't find device with uuid KGf6QK-1LrJ-JDaA-bJJY-pmLb-l9eV-LEXgT2.
Physical volume "/dev/vda1" successfully created
vgcfgrestore vg_data
Restored volume group vg_data
lvchange --resync vg_data/lv_r10
Do you really want to deactivate logical volume lv_r10 to resync it? [y/n]: y
lvs -a -o +devices
LV VG Attr LSize Pool Origin Data% Move Log Copy% Convert Devices
lv_r10 vg_data rwi-a-r-- 3.00g 100.00 lv_r10_rimage_0(0),lv_r10_rimage_1(0),lv_r10_rimage_2(0),lv_r10_rimage_3(0)
[lv_r10_rimage_0] vg_data iwi-aor-- 1.50g /dev/vda1(2)
[lv_r10_rimage_1] vg_data iwi-aor-- 1.50g /dev/vdb1(2)
[lv_r10_rimage_2] vg_data iwi-aor-- 1.50g /dev/vdc1(2)
[lv_r10_rimage_3] vg_data iwi-aor-- 1.50g /dev/vdd1(2)
[lv_r10_rmeta_0] vg_data ewi-aor-- 4.00m /dev/vda1(1)
[lv_r10_rmeta_1] vg_data ewi-aor-- 4.00m /dev/vdb1(1)
[lv_r10_rmeta_2] vg_data ewi-aor-- 4.00m /dev/vdc1(1)
[lv_r10_rmeta_3] vg_data ewi-aor-- 4.00m /dev/vdd1(1)
mount -t ext4 /dev/vg_data/lv_r10 /mnt/r10/
mount: wrong fs type, bad option, bad superblock on /dev/mapper/vg_data-lv_r10,
missing codepage or helper program, or other error
In some cases useful info is found in syslog - try
dmesg | tail or so
dmesg | tail
-------------
[ 715.361985] EXT4-fs (dm-8): VFS: Can't find ext4 filesystem
[ 715.362248] EXT4-fs (dm-8): VFS: Can't find ext4 filesystem
[ 715.362548] EXT4-fs (dm-8): VFS: Can't find ext4 filesystem
[ 715.362846] FAT-fs (dm-8): bogus number of reserved sectors
[ 715.362933] FAT-fs (dm-8): Can't find a valid FAT filesystem
[ 729.843473] EXT4-fs (dm-8): VFS: Can't find ext4 filesystem
As you can see, after more then one disk failure and raid repair , I lost the file system on the raid 10 volume. Please, suggest what I am doing wrong.Thanks.
Pavlik
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https://www.redhat.com/mailman/listinfo/linux-lvm
read the LVM HOW-TO at http://tldp.org/HOWTO/LVM-HOWTO/
--
.~.
/V\
// \\
/( )\
^`~'^
emmanuel segura
2016-02-02 16:50:34 UTC
Permalink
Using the lvm version "LVM version: 2.02.141(2)-git (2016-01-25)"
the space is not begin allocate twice when you try to recover or
replace the failed device with a new one.

https://git.fedorahosted.org/cgit/lvm2.git/commit/?id=b33d7586e7f629818e881e26677f4431a47d50b5

Anyway if you have a failing disk, you can recover in this way:

lvs -o seg_pe_ranges,lv_name,stripes -a vgraid10
PE Ranges
LV #Str
lv_r10_rimage_0:0-255 lv_r10_rimage_1:0-255 lv_r10_rimage_2:0-255
lv_r10_rimage_3:0-255 lv_r10 4
/dev/sdb:1-256
[lv_r10_rimage_0] 1
/dev/sdc:1-256
[lv_r10_rimage_1] 1
/dev/sdd:1-256
[lv_r10_rimage_2] 1
/dev/sde:1-256
[lv_r10_rimage_3] 1
/dev/sdb:0-0
[lv_r10_rmeta_0] 1
/dev/sdc:0-0
[lv_r10_rmeta_1] 1
/dev/sdd:0-0
[lv_r10_rmeta_2] 1
/dev/sde:0-0
[lv_r10_rmeta_3] 1

echo 1 > /sys/block/sdb/device/delete

vgextend vgraid10 /dev/sdf
lvconvert --repair vgraid10/lv_r10 /dev/sdf



lvs -o seg_pe_ranges,lv_name,stripes -a vgraid10
Couldn't find device with uuid zEcc1n-172G-lNA9-ucC2-JJRx-kZnX-xx7tAW.
PE Ranges
LV #Str
lv_r10_rimage_0:0-255 lv_r10_rimage_1:0-255 lv_r10_rimage_2:0-255
lv_r10_rimage_3:0-255 lv_r10 4
/dev/sdf:1-256
[lv_r10_rimage_0] 1
/dev/sdc:1-256
[lv_r10_rimage_1] 1
/dev/sdd:1-256
[lv_r10_rimage_2] 1
/dev/sde:1-256
[lv_r10_rimage_3] 1
/dev/sdf:0-0
[lv_r10_rmeta_0] 1
/dev/sdc:0-0
[lv_r10_rmeta_1] 1
/dev/sdd:0-0
[lv_r10_rmeta_2] 1
/dev/sde:0-0
[lv_r10_rmeta_3] 1
New lvm version 2.02.111(2) (2014-09-01)
Library version: 1.02.90 (2014-09-01)
Driver version: 4.27.0
However it seems to me that the command "lvchange --syncaction repair vg_data/lv_r10" does not perform a resync if there are no mismatches.
## Created the same LV as before, shut down, replace disk, start up again ###
lvs -a -o +devices,raid_mismatch_count,raid_sync_action
Couldn't find device with uuid f0M1di-y7Fy-TZZg-3RO3-kJsA-fWEi-MoD2mt.
LV VG Attr LSize Pool Origin Data% Meta% Move Log Cpy%Sync Convert Devices Mismatches SyncAction
lv_r10 vg_data rwi-a-r-p- 3.00g 100.00 lv_r10_rimage_0(0),lv_r10_rimage_1(0),lv_r10_rimage_2(0),lv_r10_rimage_3(0) 0 idle
[lv_r10_rimage_0] vg_data iwi-aor--- 1.50g /dev/vda1(2)
[lv_r10_rimage_1] vg_data iwi-a-r-p- 1.50g unknown device(2)
[lv_r10_rimage_2] vg_data iwi-aor--- 1.50g /dev/vdc1(2)
[lv_r10_rimage_3] vg_data iwi-aor--- 1.50g /dev/vdd1(2)
[lv_r10_rmeta_0] vg_data ewi-aor--- 4.00m /dev/vda1(1)
[lv_r10_rmeta_1] vg_data ewi-a-r-p- 4.00m unknown device(1)
[lv_r10_rmeta_2] vg_data ewi-aor--- 4.00m /dev/vdc1(1)
[lv_r10_rmeta_3] vg_data ewi-aor--- 4.00m /dev/vdd1(1)
pvs
Couldn't find device with uuid f0M1di-y7Fy-TZZg-3RO3-kJsA-fWEi-MoD2mt.
PV VG Fmt Attr PSize PFree
/dev/vda1 vg_data lvm2 a-- 8.00g 6.49g
/dev/vdc1 vg_data lvm2 a-- 8.00g 6.49g
/dev/vdd1 vg_data lvm2 a-- 8.00g 6.49g
unknown device vg_data lvm2 a-m 8.00g 6.49g
grep description /etc/lvm/backup/vg_data
description = "Created *after* executing 'lvcreate --type raid10 -L3g -i 2 -I 256 -n lv_r10 vg_data /dev/vda1:1-900 /dev/vdb1:1-900 /dev/vdc1:1-900 /dev/vdd1:1-900'"
pvcreate --uuid f0M1di-y7Fy-TZZg-3RO3-kJsA-fWEi-MoD2mt --restorefile /etc/lvm/backup/vg_data /dev/vdb1
Couldn't find device with uuid f0M1di-y7Fy-TZZg-3RO3-kJsA-fWEi-MoD2mt.
Physical volume "/dev/vdb1" successfully created
vgcfgrestore vg_data
Restored volume group vg_data
lvchange --syncaction repair vg_data/lv_r10
dmesg | tail
------------
[ 324.454722] md: requested-resync of RAID array mdX
[ 324.454725] md: minimum _guaranteed_ speed: 1000 KB/sec/disk.
[ 324.454727] md: using maximum available idle IO bandwidth (but not more than 200000 KB/sec) for requested-resync.
[ 324.454729] md: using 128k window, over a total of 3145728k.
[ 324.454882] md: mdX: requested-resync done.
### Here I think the new PV did not receive any data
### shut down , replace vda , start the system###
grep description /etc/lvm/backup/vg_data
description = "Created *after* executing 'vgscan'"
pvcreate --uuid zjJVEj-VIKe-oe0Z-W1CF-edfj-16n2-oiAyID --restorefile /etc/lvm/backup/vg_data /dev/vda1
Couldn't find device with uuid zjJVEj-VIKe-oe0Z-W1CF-edfj-16n2-oiAyID.
Physical volume "/dev/vda1" successfully created
vgcfgrestore vg_data
Restored volume group vg_data
lvchange --syncaction repair vg_data/lv_r10
Unable to send message to an inactive logical volume.
dmesg | tail
-------------
[ 374.959535] device-mapper: raid: Failed to read superblock of device at position 0
[ 374.959577] device-mapper: raid: New device injected into existing array without 'rebuild' parameter specified
[ 374.959621] device-mapper: table: 252:10: raid: Unable to assemble array: Invalid superblocks
[ 374.959656] device-mapper: ioctl: error adding target to table
### I gave another try to my previous procedure with "lvchange --resync vg_data/lv_r10", but this again destroyed the file system, even now with the newer LVM version.
### Also the test with lvconvert --repair produced the same result as before.
Please, advice.
Pavlik
----- Original Message -----
Sent: Monday, February 1, 2016 1:22 PM
Subject: Re: [linux-lvm] Raid 10 - recovery after a disk failure
--[raid]syncaction {check|repair}
This argument is used to initiate various RAID
synchronization operations. The check and repair options provide a
way to check the integrity of a RAID log‐
ical volume (often referred to as "scrubbing").
These options cause the RAID logical volume to read all of the data
and parity blocks in the array and
check for any discrepancies (e.g. mismatches between
mirrors or incorrect parity values). If check is used, the
discrepancies will be counted but not
repaired. If repair is used, the discrepancies will
be corrected as they are encountered. The 'lvs' command can be used
to show the number of discrepan‐
cies found or repaired.
maybe --resync is for mirror and you are using raid
--resync
Forces the complete resynchronization of a mirror. In
normal circumstances you should not need this option because
synchronization happens automatically.
Data is read from the primary mirror device and copied
to the others, so this can take a considerable amount of time - and
during this time you are without
a complete redundant copy of your data.
--
.~.
/V\
// \\
/( )\
^`~'^
Pavlik Kirilov
2016-02-02 23:20:10 UTC
Permalink
Thank you for helping me out with this. I am glad the issue was fixed in the newer version of LVM.

Regards,

Pavlik




----- Original Message -----
From: emmanuel segura <***@gmail.com>
To: LVM general discussion and development <linux-***@redhat.com>
Sent: Tuesday, February 2, 2016 11:50 AM
Subject: Re: [linux-lvm] Raid 10 - recovery after a disk failure

Using the lvm version "LVM version: 2.02.141(2)-git (2016-01-25)"
the space is not begin allocate twice when you try to recover or
replace the failed device with a new one.

https://git.fedorahosted.org/cgit/lvm2.git/commit/?id=b33d7586e7f629818e881e26677f4431a47d50b5

Anyway if you have a failing disk, you can recover in this way:

lvs -o seg_pe_ranges,lv_name,stripes -a vgraid10
PE Ranges
LV #Str
lv_r10_rimage_0:0-255 lv_r10_rimage_1:0-255 lv_r10_rimage_2:0-255
lv_r10_rimage_3:0-255 lv_r10 4
/dev/sdb:1-256
[lv_r10_rimage_0] 1
/dev/sdc:1-256
[lv_r10_rimage_1] 1
/dev/sdd:1-256
[lv_r10_rimage_2] 1
/dev/sde:1-256
[lv_r10_rimage_3] 1
/dev/sdb:0-0
[lv_r10_rmeta_0] 1
/dev/sdc:0-0
[lv_r10_rmeta_1] 1
/dev/sdd:0-0
[lv_r10_rmeta_2] 1
/dev/sde:0-0
[lv_r10_rmeta_3] 1

echo 1 > /sys/block/vdb/device/delete

vgextend vgraid10 /dev/sdf
lvconvert --repair vgraid10/lv_r10 /dev/sdf



lvs -o seg_pe_ranges,lv_name,stripes -a vgraid10
Couldn't find device with uuid zEcc1n-172G-lNA9-ucC2-JJRx-kZnX-xx7tAW.
PE Ranges
LV #Str
lv_r10_rimage_0:0-255 lv_r10_rimage_1:0-255 lv_r10_rimage_2:0-255
lv_r10_rimage_3:0-255 lv_r10 4
/dev/sdf:1-256
[lv_r10_rimage_0] 1
/dev/sdc:1-256
[lv_r10_rimage_1] 1
/dev/sdd:1-256
[lv_r10_rimage_2] 1
/dev/sde:1-256
[lv_r10_rimage_3] 1
/dev/sdf:0-0
[lv_r10_rmeta_0] 1
/dev/sdc:0-0
[lv_r10_rmeta_1] 1
/dev/sdd:0-0
[lv_r10_rmeta_2] 1
/dev/sde:0-0
[lv_r10_rmeta_3] 1
New lvm version 2.02.111(2) (2014-09-01)
Library version: 1.02.90 (2014-09-01)
Driver version: 4.27.0
However it seems to me that the command "lvchange --syncaction repair vg_data/lv_r10" does not perform a resync if there are no mismatches.
## Created the same LV as before, shut down, replace disk, start up again ###
lvs -a -o +devices,raid_mismatch_count,raid_sync_action
Couldn't find device with uuid f0M1di-y7Fy-TZZg-3RO3-kJsA-fWEi-MoD2mt.
LV VG Attr LSize Pool Origin Data% Meta% Move Log Cpy%Sync Convert Devices Mismatches SyncAction
lv_r10 vg_data rwi-a-r-p- 3.00g 100.00 lv_r10_rimage_0(0),lv_r10_rimage_1(0),lv_r10_rimage_2(0),lv_r10_rimage_3(0) 0 idle
[lv_r10_rimage_0] vg_data iwi-aor--- 1.50g /dev/vda1(2)
[lv_r10_rimage_1] vg_data iwi-a-r-p- 1.50g unknown device(2)
[lv_r10_rimage_2] vg_data iwi-aor--- 1.50g /dev/vdc1(2)
[lv_r10_rimage_3] vg_data iwi-aor--- 1.50g /dev/vdd1(2)
[lv_r10_rmeta_0] vg_data ewi-aor--- 4.00m /dev/vda1(1)
[lv_r10_rmeta_1] vg_data ewi-a-r-p- 4.00m unknown device(1)
[lv_r10_rmeta_2] vg_data ewi-aor--- 4.00m /dev/vdc1(1)
[lv_r10_rmeta_3] vg_data ewi-aor--- 4.00m /dev/vdd1(1)
pvs
Couldn't find device with uuid f0M1di-y7Fy-TZZg-3RO3-kJsA-fWEi-MoD2mt.
PV VG Fmt Attr PSize PFree
/dev/vda1 vg_data lvm2 a-- 8.00g 6.49g
/dev/vdc1 vg_data lvm2 a-- 8.00g 6.49g
/dev/vdd1 vg_data lvm2 a-- 8.00g 6.49g
unknown device vg_data lvm2 a-m 8.00g 6.49g
grep description /etc/lvm/backup/vg_data
description = "Created *after* executing 'lvcreate --type raid10 -L3g -i 2 -I 256 -n lv_r10 vg_data /dev/vda1:1-900 /dev/vdb1:1-900 /dev/vdc1:1-900 /dev/vdd1:1-900'"
pvcreate --uuid f0M1di-y7Fy-TZZg-3RO3-kJsA-fWEi-MoD2mt --restorefile /etc/lvm/backup/vg_data /dev/vdb1
Couldn't find device with uuid f0M1di-y7Fy-TZZg-3RO3-kJsA-fWEi-MoD2mt.
Physical volume "/dev/vdb1" successfully created
vgcfgrestore vg_data
Restored volume group vg_data
lvchange --syncaction repair vg_data/lv_r10
dmesg | tail
------------
[ 324.454722] md: requested-resync of RAID array mdX
[ 324.454725] md: minimum _guaranteed_ speed: 1000 KB/sec/disk.
[ 324.454727] md: using maximum available idle IO bandwidth (but not more than 200000 KB/sec) for requested-resync.
[ 324.454729] md: using 128k window, over a total of 3145728k.
[ 324.454882] md: mdX: requested-resync done.
### Here I think the new PV did not receive any data
### shut down , replace vda , start the system###
grep description /etc/lvm/backup/vg_data
description = "Created *after* executing 'vgscan'"
pvcreate --uuid zjJVEj-VIKe-oe0Z-W1CF-edfj-16n2-oiAyID --restorefile /etc/lvm/backup/vg_data /dev/vda1
Couldn't find device with uuid zjJVEj-VIKe-oe0Z-W1CF-edfj-16n2-oiAyID.
Physical volume "/dev/vda1" successfully created
vgcfgrestore vg_data
Restored volume group vg_data
lvchange --syncaction repair vg_data/lv_r10
Unable to send message to an inactive logical volume.
dmesg | tail
-------------
[ 374.959535] device-mapper: raid: Failed to read superblock of device at position 0
[ 374.959577] device-mapper: raid: New device injected into existing array without 'rebuild' parameter specified
[ 374.959621] device-mapper: table: 252:10: raid: Unable to assemble array: Invalid superblocks
[ 374.959656] device-mapper: ioctl: error adding target to table
### I gave another try to my previous procedure with "lvchange --resync vg_data/lv_r10", but this again destroyed the file system, even now with the newer LVM version.
### Also the test with lvconvert --repair produced the same result as before.
Please, advice.
Pavlik
----- Original Message -----
Sent: Monday, February 1, 2016 1:22 PM
Subject: Re: [linux-lvm] Raid 10 - recovery after a disk failure
--[raid]syncaction {check|repair}
This argument is used to initiate various RAID
synchronization operations. The check and repair options provide a
way to check the integrity of a RAID log‐
ical volume (often referred to as "scrubbing").
These options cause the RAID logical volume to read all of the data
and parity blocks in the array and
check for any discrepancies (e.g. mismatches between
mirrors or incorrect parity values). If check is used, the
discrepancies will be counted but not
repaired. If repair is used, the discrepancies will
be corrected as they are encountered. The 'lvs' command can be used
to show the number of discrepan‐
cies found or repaired.
maybe --resync is for mirror and you are using raid
--resync
Forces the complete resynchronization of a mirror. In
normal circumstances you should not need this option because
synchronization happens automatically.
Data is read from the primary mirror device and copied
to the others, so this can take a considerable amount of time - and
during this time you are without
a complete redundant copy of your data.
--
.~.
/V\
// \\
/( )\
^`~'^

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