When BTRFS is not awesome, except when it isn't

[GreyGeek]

I've been using BTRFS going on 5 years (this September) without problems. My ATA Toshiba 750GB HD, my most recent HD purchase from a year ago, has been throwing bad sectors. I don't know how many sectors are in its reserve space which it can throw and still be good, but its "Relocated sectors count" is marked "Warning" with 16, according to Smart. And, its power on time is marked at 199 million hours. I'm no HD expert and I don't know what much of the Smart data really means, but in anticipation of problems I began to review BTRFS recovery procedures and making posts of what I've been reading as a handy memo tool.

Also, as soon as Neon User Edtion 18.04 comes out I will be testing the "do-release-upgrade" method of moving to the new release. And, I'll be taking the Toshiba drive out and replacing it with a 250GB Samsung EVO 860 SSD, thanks to Oshunluver, as my primary drive. Also, because my data is 110GB I will be utilizing zstd compression on the SSD to give it the appearance of a 750GB HD. Zstd's optimum compression is 3:1, so I've read, and it is the fastest algorithm.

Today, I discovered this very short but informative video about the topic:
BTRFS is awesome, except when it isn't

which explains in a short 15 minutes what to do AND NOT to do if things go south with your Btrfs installation. It uses openSUSE as the basis for the discussion but there is nothing in the video which cannot be used by a *buntu distro set up with Btrfs as the <ROOT_FS>.

An aside: openSUSE has adopted a setup with Snapper that I adopted three years ago when I was experimenting with it. It disabled the "Timeline" feature, which means that Snapper is set for SINGLETON snapshots. Snapper is a pain to configure but after configuration it is an OK CLI tool. My advice is to use Timeshift, if you want a snapshot and rollback GUI. And remember, a snapshot is not a backup unless you send & receive it to an outside destination.

[dibl]

Good video, and good advice. The only time that I can recall that BTRFS "check" reported a problem, BTRFS "scrub" fixed it, just as he says. That was in 2013, on 4-year old hardware, and I promptly bought another pair of WD1000 drives, made a new BTRFS filesystem on them, and moved my data to the new filesystem. That BTRFS filesystem ran 24/7/365 until a couple of weeks ago, when my newly-built system was ready to take over the job. I consider 5 years of faithful service a pretty good result for consumer electronics. As far as I know there's nothing wrong with the old hardware today -- I'll put in on craigslist in few weeks after my new system proves its reliability.

[GreyGeek]

Old hardware is reliable indeed!
My Acer V3-771G was made in 2012 and is working perfectly.

[dibl]

Old hardware is reliable indeed!
My Acer V3-771G was made in 2012 and is working perfectly.

I'd say depends on what you mean by "reliable". Do I know about ancient hardware? YES, I do -- check the BIOS date on this e-Machines dinosaur:

root@decembersid:/# inxi -Fz                 
System:
Host: decembersid Kernel: 4.17.8-towo.1-siduction-amd64 x86_64 bits: 64 
Desktop: KDE Plasma 5.13.2 
Distro: siduction 13.2.1 December - kde - (201401272125) 
Machine:
Type: N/A System: h product: �G��� ��G��� �f��6� v: h serial: <filter> 
Mobo: N/A model:  serial: <filter> BIOS: Intel 
v: CF94510J.15A.0028.2006.1213.1629 date: 12/13/2006 
CPU:
Topology: Dual Core model: Intel Pentium D bits: 64 type: MCP L2 cache: 1024 KiB 
Speed: 2795 MHz min/max: N/A Core speeds (MHz): 1: 2795 2: 2795 
Graphics:
Card-1: Intel 82945G/GZ Integrated Graphics driver: i915 v: kernel 
Display: x11 server: X.Org 1.20.0 driver: intel resolution: 1440x900~60Hz 
OpenGL: renderer: Mesa DRI Intel 945G v: 1.4 Mesa 18.1.4 
Audio:
Card-1: Intel NM10/ICH7 Family High Definition Audio driver: snd_hda_intel 
Sound Server: ALSA v: k4.17.8-towo.1-siduction-amd64 
Network:
Card-1: Intel PRO/100 VE Network driver: e100 
IF: eth1 state: down mac: <filter> 
Card-2: TP-Link TL-WN821N v3 / TL-WN822N v2 802.11n [Atheros AR7010+AR9287] 
type: USB driver: ath9k_htc 
IF: wlan0 state: up mac: <filter> 
Drives:
Local Storage: total: 232.89 GiB used: 10.63 GiB (4.6%) 
ID-1: /dev/sda vendor: Hitachi model: HDT725025VLA380 size: 232.89 GiB 
RAID:
Hardware-1: Intel 82801GR/GDH (ICH7R/ICH7DH) SATA Controller [RAID mode] 
driver: ahci 
Partition:
ID-1: / size: 21.07 GiB used: 10.58 GiB (50.2%) fs: ext4 dev: /dev/sda1 
ID-2: swap-1 size: 2.00 GiB used: 0 KiB (0.0%) fs: swap dev: /dev/sda2 
Sensors:
Message: No sensors data was found. Is sensors configured? 
Info:
Processes: 156 Uptime: 4m Memory: 1.94 GiB used: 530.2 MiB (26.7%) Shell: bash 
inxi: 3.0.18

And get a load of its hard disk drive:

root@decembersid:/# smartctl -ia /dev/sda
smartctl 6.6 2016-05-31 r4324 [x86_64-linux-4.17.8-towo.1-siduction-amd64] (local build)
Copyright (C) 2002-16, Bruce Allen, Christian Franke, www.smartmontools.org

=== START OF INFORMATION SECTION ===
Model Family:     Hitachi Deskstar T7K500
Device Model:     Hitachi HDT725025VLA380
Serial Number:    VFC100R1CUURVM
LU WWN Device Id: 5 000cca 210cbbde4
Firmware Version: V5DOA52A
User Capacity:    250,059,350,016 bytes [250 GB]
Sector Size:      512 bytes logical/physical
Device is:        In smartctl database [for details use: -P show]
ATA Version is:   ATA/ATAPI-7 T13/1532D revision 1
Local Time is:    Wed Jul 18 19:53:57 2018 EDT
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:                ( 4949) seconds.
Offline data collection
capabilities:                    (0x5b) SMART execute Offline immediate.
                                   Auto Offline data collection on/off support.
                                   Suspend Offline collection upon new
                                   command.
                                   Offline surface scan supported.
                                   Self-test supported.
                                   No 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:        (   1) minutes.
Extended self-test routine
recommended polling time:        (  83) minutes.
SCT capabilities:              (0x003f) 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     0x000b   100   100   016    Pre-fail  Always       -       0
2 Throughput_Performance  0x0005   100   100   050    Pre-fail  Offline      -       0
3 Spin_Up_Time            0x0007   106   106   024    Pre-fail  Always       -       352 (Average 352)
4 Start_Stop_Count        0x0012   100   100   000    Old_age   Always       -       512
5 Reallocated_Sector_Ct   0x0033   100   100   005    Pre-fail  Always       -       0
7 Seek_Error_Rate         0x000b   100   100   067    Pre-fail  Always       -       0
8 Seek_Time_Performance   0x0005   100   100   020    Pre-fail  Offline      -       0
9 Power_On_Hours          0x0012   092   092   000    Old_age   Always       -       58312
10 Spin_Retry_Count        0x0013   100   100   060    Pre-fail  Always       -       0
12 Power_Cycle_Count       0x0032   100   100   000    Old_age   Always       -       511
192 Power-Off_Retract_Count 0x0032   098   098   000    Old_age   Always       -       2917
193 Load_Cycle_Count        0x0012   098   098   000    Old_age   Always       -       2917
194 Temperature_Celsius     0x0002   153   153   000    Old_age   Always       -       39 (Min/Max 9/47)
196 Reallocated_Event_Count 0x0032   100   100   000    Old_age   Always       -       0
197 Current_Pending_Sector  0x0022   100   100   000    Old_age   Always       -       0
198 Offline_Uncorrectable   0x0008   100   100   000    Old_age   Offline      -       0
199 UDMA_CRC_Error_Count    0x000a   200   253   000    Old_age   Always       -       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%     56174         -
# 2  Extended offline    Completed without error       00%     55969         -

But, there is not one important data file on that old POS. It is just for guests who need to use the internet while at my house. One day it will blink out like a lightbulb, but since it goes for weeks without being powered on, who knows when that day will come? I keep it updated with new kernels and KDE/Plasma packages, and it chugs along and continues to do the job, albeit slowly ... LOL

[GreyGeek]

5 Reallocated_Sector_Ct 0x0033 100 100 005 Pre-fail Always - 0

Not bad for a 12 year old drive. My LESS THAN ONE YEAR old Toshiba drive has 16 relocated sectors!
I expect it to fail within a year or two, which is why I am pulling it out and replacing it with an SSD.