Recover RAID

Question

Hi all!
I have a dual RAID1 setup consisting of 4 drives (4 TB each) setup like this;
/dev/md0 => sdb1, sda1
/dev/md1 => sdd1, sdc1
On top of this I used LVM to create a volumegroup spanning over both arrays;
--- Physical volume ---
PV Name /dev/md0
VG Name MediaGroupArray
PV Size 3.64 TiB / not usable 2.81 MiB
Allocatable yes (but full)
PE Size 4.00 MiB
Total PE 953829
Free PE 0
Allocated PE 953829
PV UUID xdFHBj-y5ZJ-qKoE-M9PG-pgjT-EceT-G7lvxX
--- Physical volume ---
PV Name /dev/md1
VG Name MediaGroupArray
PV Size 3.64 TiB / not usable 2.81 MiB
Allocatable yes (but full)
PE Size 4.00 MiB
Total PE 953829
Free PE 0
Allocated PE 953829
PV UUID XAWTzZ-n3qj-IIoU-HHM2-0dpB-U846-EvVMjq
--- Volume group ---
VG Name MediaGroupArray
System ID
Format lvm2
Metadata Areas 2
Metadata Sequence No 3
VG Access read/write
VG Status resizable
MAX LV 0
Cur LV 2
Open LV 2
Max PV 0
Cur PV 2
Act PV 2
VG Size 7.28 TiB
PE Size 4.00 MiB
Total PE 1907658
Alloc PE / Size 1907658 / 7.28 TiB
Free PE / Size 0 / 0
VG UUID GyUJrh-qXvp-klwy-M7ps-5mqQ-WMiZ-cs3BQg
And in this volumegroup I then created two logical volumes
--- Logical volume ---
LV Path /dev/MediaGroupArray/lvsrv
LV Name lvsrv
VG Name MediaGroupArray
LV UUID fWPLSu-qGoL-Xec6-VH82-yKr4-MmSs-FWTgkM
LV Write Access read/write
LV Creation host, time angelica, 2014-07-30 21:01:33 +0200
LV Status available
# open 1
LV Size 100.00 GiB
Current LE 25600
Segments 1
Allocation inherit
Read ahead sectors auto
- currently set to 256
Block device 253:0
--- Logical volume ---
LV Path /dev/MediaGroupArray/lvmedia
LV Name lvmedia
VG Name MediaGroupArray
LV UUID V940i2-e9VJ-8UTl-jF0k-EMDr-jJA0-6d7R4G
LV Write Access read/write
LV Creation host, time angelica, 2014-07-30 21:05:32 +0200
LV Status available
# open 1
LV Size 7.18 TiB
Current LE 1882058
Segments 2
Allocation inherit
Read ahead sectors auto
- currently set to 256
Block device 253:1
This have been working great for little over a month, until I received an email about the /dev/md0 array being degraded!
Checking /proc/mdstat
Personalities : [raid1]
md1 : active raid1 sdd1[1] sdc1[0]
3906886464 blocks super 1.2 [2/2] [UU]
bitmap: 0/30 pages [0KB], 65536KB chunk
md0 : active raid1 sdb1[1]
3906886464 blocks super 1.2 [2/1] [_U]
bitmap: 7/30 pages [28KB], 65536KB chunk
unused devices: <none>
shows that /dev/sda had fell out of the array. When trying to reassemble the RAID mdadm told me something along the line of "no such partition", sorry not able to give anything more specific since I didn't write it down...
Anyhow when I checked the partition table for all the drives I found that all the other drives showed one big partition of "Linux RAID" just as it was setup. However /dev/sda suddenly had one partition of type "Linux" that spanned just about half the drive and the rest was marked as free space. What worse was that gdisk told me that the GPT-table was corrupt and its attempts to fix it didn't work. Again sorry about the lack of details, didn't write this down either.
To try and fix it I decided wipe out the drive and then create a new partition followed by re adding it to the RAID, however i then got the following message:
sudo gdisk /dev/sda
GPT fdisk (gdisk) version 0.8.10
Partition table scan:
MBR: not present
BSD: not present
APM: not present
GPT: not present
Creating new GPT entries.
Command (? for help): n
Partition number (1-128, default 1):
First sector (34-7814035021, default = 2048) or {+-}size{KMGTP}:
Last sector (2048-7814035021, default = 7814035021) or {+-}size{KMGTP}:
Current type is 'Linux filesystem'
Hex code or GUID (L to show codes, Enter = 8300): fd00
Changed type of partition to 'Linux RAID'
Command (? for help): w
Final checks complete. About to write GPT data. THIS WILL OVERWRITE EXISTING
PARTITIONS!!
Do you want to proceed? (Y/N): y
OK; writing new GUID partition table (GPT) to /dev/sda.
The operation has completed successfully.
[evilangel@angelica ~]$ sudo mdadm --add /dev/md0 /dev/sda1
mdadm: /dev/sda1 not large enough to join array
Comparing the sizes of the different drives I now see that the working drives are "4000787030016" bytes long (as they should be) but sda is now "4000785948160", meaning about 10MB of the physical size of the drive has disappeared. Since the size of the partition is also smaller I understand why mdadm can't add it to the RAID (also kicking myself for not following the wiki and leaving 100MB of free space at the end of the drive...).
I tried to run a long self test using SMART and then checking the output but I can't see anything:
[evilangel@angelica ~]$ sudo smartctl --all /dev/sda
[sudo] password for evilangel:
smartctl 6.3 2014-07-26 r3976 [x86_64-linux-3.16.1-1-ARCH] (local build)
Copyright (C) 2002-14, Bruce Allen, Christian Franke, www.smartmontools.org
=== START OF INFORMATION SECTION ===
Model Family: Western Digital Red (AF)
Device Model: WDC WD40EFRX-68WT0N0
Serial Number: WD-WCC4EJUPNAR5
LU WWN Device Id: 5 0014ee 20a85f85c
Firmware Version: 80.00A80
User Capacity: 4,000,785,948,160 bytes [4.00 TB]
Sector Sizes: 512 bytes logical, 4096 bytes physical
Rotation Rate: 5400 rpm
Device is: In smartctl database [for details use: -P show]
ATA Version is: ACS-2 (minor revision not indicated)
SATA Version is: SATA 3.0, 6.0 Gb/s (current: 3.0 Gb/s)
Local Time is: Tue Sep 2 08:49:31 2014 CEST
SMART support is: Available - device has SMART capability.
SMART support is: Enabled
=== START OF READ SMART DATA SECTION ===
SMART overall-health self-assessment test result: PASSED
General SMART Values:
Offline data collection status: (0x00) Offline data collection activity
was never started.
Auto Offline Data Collection: Disabled.
Self-test execution status: ( 0) The previous self-test routine completed
without error or no self-test has ever
been run.
Total time to complete Offline
data collection: (51720) seconds.
Offline data collection
capabilities: (0x7b) SMART execute Offline immediate.
Auto Offline data collection on/off support.
Suspend Offline collection upon new
command.
Offline surface scan supported.
Self-test supported.
Conveyance Self-test supported.
Selective Self-test supported.
SMART capabilities: (0x0003) Saves SMART data before entering
power-saving mode.
Supports SMART auto save timer.
Error logging capability: (0x01) Error logging supported.
General Purpose Logging supported.
Short self-test routine
recommended polling time: ( 2) minutes.
Extended self-test routine
recommended polling time: ( 517) minutes.
Conveyance self-test routine
recommended polling time: ( 5) minutes.
SCT capabilities: (0x703d) SCT Status supported.
SCT Error Recovery Control supported.
SCT Feature Control supported.
SCT Data Table supported.
SMART Attributes Data Structure revision number: 16
Vendor Specific SMART Attributes with Thresholds:
ID# ATTRIBUTE_NAME FLAG VALUE WORST THRESH TYPE UPDATED WHEN_FAILED RAW_VALUE
1 Raw_Read_Error_Rate 0x002f 200 200 051 Pre-fail Always - 0
3 Spin_Up_Time 0x0027 185 185 021 Pre-fail Always - 7725
4 Start_Stop_Count 0x0032 100 100 000 Old_age Always - 7
5 Reallocated_Sector_Ct 0x0033 200 200 140 Pre-fail Always - 0
7 Seek_Error_Rate 0x002e 200 200 000 Old_age Always - 0
9 Power_On_Hours 0x0032 099 099 000 Old_age Always - 773
10 Spin_Retry_Count 0x0032 100 253 000 Old_age Always - 0
11 Calibration_Retry_Count 0x0032 100 253 000 Old_age Always - 0
12 Power_Cycle_Count 0x0032 100 100 000 Old_age Always - 7
192 Power-Off_Retract_Count 0x0032 200 200 000 Old_age Always - 3
193 Load_Cycle_Count 0x0032 200 200 000 Old_age Always - 19
194 Temperature_Celsius 0x0022 121 097 000 Old_age Always - 31
196 Reallocated_Event_Count 0x0032 200 200 000 Old_age Always - 0
197 Current_Pending_Sector 0x0032 200 200 000 Old_age Always - 0
198 Offline_Uncorrectable 0x0030 100 253 000 Old_age Offline - 0
199 UDMA_CRC_Error_Count 0x0032 200 200 000 Old_age Always - 0
200 Multi_Zone_Error_Rate 0x0008 200 200 000 Old_age Offline - 0
SMART Error Log Version: 1
No Errors Logged
SMART Self-test log structure revision number 1
Num Test_Description Status Remaining LifeTime(hours) LBA_of_first_error
# 1 Extended offline Completed without error 00% 764 -
SMART Selective self-test log data structure revision number 1
SPAN MIN_LBA MAX_LBA CURRENT_TEST_STATUS
1 0 0 Not_testing
2 0 0 Not_testing
3 0 0 Not_testing
4 0 0 Not_testing
5 0 0 Not_testing
Selective self-test flags (0x0):
After scanning selected spans, do NOT read-scan remainder of disk.
If Selective self-test is pending on power-up, resume after 0 minute delay.
Now to the questions.. what happened to make the drive fall out in the first place? But more important how can I fix it?
Also is it normal for drives to shrink like this? All of the drives where brand new when they went in to the array...

Answer 1

Ah I see now, got a bit confused there.
You certainly have a point there, guess I just have to consider the drive bad and replace it. Wonder if I can make a point against the reseller, one would feel a new drive (especially since it was marked as a "24/7 NAS Drive") should last a bit long before sectors start dying. Worth a shoot at least...