Comparison of Ext4 and Btrfs

[oshunluvr]

I have no clue as to what the "dos" partition was, since I deleted the only partition on the HD

BTRFS sanity check - it detected the partition table and prevented you from "accidentally" formatting a drive that was being used. Remember when you apply BTRFS formatting to an entire device, it uses the partition table and boot record space along with everything else.

[GreyGeek]

Comparison of Ext4 and Btrfs

BTRFS sanity check - it detected the partition table and prevented you from "accidentally" formatting a drive that was being used. Remember when you apply BTRFS formatting to an entire device, it uses the partition table and boot record space along with everything else.

Ah, so deleting the partition does not delete the partition table? I did not know that, after all these years. I thought creating the partition only created the table, which set the parameters for subsequent formatting, and when one deleted the partition the table was deleted as well.

[oshunluvr]

If you get a new "clean" drive or use dd to zero out an entire device, you'll have to make a partition table before you'll be able to make partitions. If you use the Kubuntu installer or Kpartition Manager and click on a totally empty drive, you get a message asking you if you want to create a new partition table. Here's what my unpartitioned btrfs server drive shows with gdisk:

[FONT=monospace][COLOR=#000000]smith@server:~$ sudo gdisk /dev/sda[/COLOR]
GPT fdisk (gdisk) version 0.8.8

Partition table scan:
 MBR: not present
 BSD: not present
 APM: not present
 GPT: not present

Creating new GPT entries.

Command (? for help): 
[/FONT]

verses a partitioned drive:

[FONT=monospace][COLOR=#000000]smith@server:~$ sudo gdisk /dev/sdb[/COLOR]
GPT fdisk (gdisk) version 0.8.8

Partition table scan:
 MBR: protective
 BSD: not present
 APM: not present
 GPT: present

Found valid GPT with protective MBR; using GPT.

Command (? for help): 

[/FONT]

[GreyGeek]

Comparison of Ext4 and Btrfs

Interesting thing happened, oshunluver. My 500gb 2.5" WD Passport USB drive failed to mount a couple of weeks ago. Fdisk-l failed to recognize its presence and neither would Kpartition, even after letting it scan overnight. Yesterday I thought that perhaps only the USB electronics were bad but the drive itself was good. I popped the cover off the drive and found that the drive was riveted to the circuit board and the USB circuitry was integrated into the drive connection circuitry. For grins and giggles I plugged it into my USB hub and fired up Kpartition. It suddenly "found" /dev/sdc and began scanning. It was stuck on 33% for several minutes but finally displayed it along with my other two drives. Apparently the problem was an intermittent connection (crack in soldering or trace?) which was re-established by my putzing around with it.

I tried to create a partition using GPT. When I applied the configuration it tried but shortly returned an error.

That's when what you wrote about "clean" HD's came to mind. I closed Kpartition and opened a Konsole. In it I issued:
sudo mkfs.btrfs /dev/sdc
It worked!
I immediately created a subvolume and cp'd some files to it from my home account. That worked nicely. I powered down last night. This morning comes the test to see if, when I plug Passport in, I can mount it to /mnt again.


Sent from my iPhone using Tapatalk

[GreyGeek]

After I booted up this morning I plugged in the Passport USB HD and tried to mount it. It failed.

1224.996256] sd 6:0:0:0: [sdc] tag#0 FAILED Result: hostbyte=DID_OK driverbyte=DRIVER_SENSE
[ 1224.996262] sd 6:0:0:0: [sdc] tag#0 Sense Key : Medium Error [current]
[ 1224.996266] sd 6:0:0:0: [sdc] tag#0 Add. Sense: Unrecovered read error
[ 1224.996271] sd 6:0:0:0: [sdc] tag#0 CDB: Read(10) 28 00 00 00 00 40 00 00 38 00
[ 1224.996274] blk_update_request: critical medium error, dev sdc, sector 64
[ 1228.350514] sd 6:0:0:0: [sdc] tag#0 FAILED Result: hostbyte=DID_OK driverbyte=DRIVER_SENSE
[ 1228.350520] sd 6:0:0:0: [sdc] tag#0 Sense Key : Medium Error [current]
[ 1228.350523] sd 6:0:0:0: [sdc] tag#0 Add. Sense: Unrecovered read error
[ 1228.350527] sd 6:0:0:0: [sdc] tag#0 CDB: Read(10) 28 00 00 00 00 80 00 00 90 00
[ 1228.350531] blk_update_request: critical medium error, dev sdc, sector 128
[ 1231.851278] sd 6:0:0:0: [sdc] tag#0 FAILED Result: hostbyte=DID_OK driverbyte=DRIVER_SENSE
[ 1231.851284] sd 6:0:0:0: [sdc] tag#0 Sense Key : Medium Error [current]
[ 1231.851287] sd 6:0:0:0: [sdc] tag#0 Add. Sense: Unrecovered read error
[ 1231.851292] sd 6:0:0:0: [sdc] tag#0 CDB: Read(10) 28 00 00 00 00 50 00 00 08 00
[ 1231.851295] blk_update_request: critical medium error, dev sdc, sector 80
[ 1231.851304] Buffer I/O error on dev sdc, logical block 10, async page read
[ 1235.236087] sd 6:0:0:0: [sdc] tag#0 FAILED Result: hostbyte=DID_OK driverbyte=DRIVER_SENSE
[ 1235.236093] sd 6:0:0:0: [sdc] tag#0 Sense Key : Medium Error [current]
[ 1235.236096] sd 6:0:0:0: [sdc] tag#0 Add. Sense: Unrecovered read error
[ 1235.236101] sd 6:0:0:0: [sdc] tag#0 CDB: Read(10) 28 00 00 00 00 50 00 00 08 00
[ 1235.236104] blk_update_request: critical medium error, dev sdc, sector 80
[ 1235.236112] Buffer I/O error on dev sdc, logical block 10, async page read
[ 1238.713461] sd 6:0:0:0: [sdc] tag#0 FAILED Result: hostbyte=DID_OK driverbyte=DRIVER_SENSE
[ 1238.713466] sd 6:0:0:0: [sdc] tag#0 Sense Key : Medium Error [current]
[ 1238.713470] sd 6:0:0:0: [sdc] tag#0 Add. Sense: Unrecovered read error
[ 1238.713474] sd 6:0:0:0: [sdc] tag#0 CDB: Read(10) 28 00 00 00 02 00 00 00 08 00
[ 1238.713478] blk_update_request: critical medium error, dev sdc, sector 512
[ 1242.081002] sd 6:0:0:0: [sdc] tag#0 FAILED Result: hostbyte=DID_OK driverbyte=DRIVER_SENSE
[ 1242.081008] sd 6:0:0:0: [sdc] tag#0 Sense Key : Medium Error [current]
[ 1242.081011] sd 6:0:0:0: [sdc] tag#0 Add. Sense: Unrecovered read error
[ 1242.081016] sd 6:0:0:0: [sdc] tag#0 CDB: Read(10) 28 00 00 00 02 00 00 00 08 00
[ 1242.081020] blk_update_request: critical medium error, dev sdc, sector 512
[ 1242.081028] Buffer I/O error on dev sdc, logical block 64, async page read
[ 1242.089252] BTRFS info (device sdc): disk space caching is enabled
[ 1242.089256] BTRFS info (device sdc): has skinny extents
[ 1245.590032] sd 6:0:0:0: [sdc] tag#0 FAILED Result: hostbyte=DID_OK driverbyte=DRIVER_SENSE
[ 1245.590037] sd 6:0:0:0: [sdc] tag#0 Sense Key : Medium Error [current]
[ 1245.590041] sd 6:0:0:0: [sdc] tag#0 Add. Sense: Unrecovered read error
[ 1245.590045] sd 6:0:0:0: [sdc] tag#0 CDB: Read(10) 28 00 00 00 a0 20 00 00 20 00
[ 1245.590048] blk_update_request: critical medium error, dev sdc, sector 40992
[ 1248.967198] sd 6:0:0:0: [sdc] tag#0 FAILED Result: hostbyte=DID_OK driverbyte=DRIVER_SENSE
[ 1248.967204] sd 6:0:0:0: [sdc] tag#0 Sense Key : Medium Error [current]
[ 1248.967208] sd 6:0:0:0: [sdc] tag#0 Add. Sense: Unrecovered read error
[ 1248.967212] sd 6:0:0:0: [sdc] tag#0 CDB: Read(10) 28 00 00 00 e0 20 00 00 20 00
[ 1248.967216] blk_update_request: critical medium error, dev sdc, sector 57376
[ 1248.967349] BTRFS error (device sdc): failed to read chunk root
[ 1249.005002] BTRFS: open_ctree failed
root@jerry-Aspire-V3-771:~#

It will always recognize the existence of an HD at /dev/sdc and I can even "mkfs.btrfs -f /dev/sdc" and it will format. But when I attempt to mount it "mount /devsdc /backup" it fails. I've tried without a partition and with both a GPT and msdos type. All fail. I have a 50% failure rate with WD Passport USB drives. In researching the problem I find it is a rule instead of an exception, regardless of OS. So, I have a 50% failure rate with WD Passport USB HDs. Lesson learned.

[oshunluvr]

Bummer your drive failed. Sure you already know this, but a pencil across a microscopic crack can restore a connection. You could just "color" over all the soldered connections with a #2 and see if it goes back to life.

I never trusted the pre-built USB drives. I have a Inateck USB 3.0 2.5" enclosure that I use. I have a 500GB laptop drive it it and it works great.

The btrfs format works because it really doesn't write to the entire disk like most formats do. It creates the headers and inode tables and then a very small amount of space for use. The "formatted" region grows dynamically as data is added. In fact, unless you use a specific tool to wipe a drive, you can reformat a btrfs file system with the files all still intact. Last time I reconfigured a btrfs partition, I had to run wipefs to clear the data inodes from the partition and free the space for use.

[GreyGeek]

The #2 pencil trick is a good idea. The problem could be temperature dependent because I let it run all night giving Kparted a chance to recognize it, which it finally did. It was after that, while it was still plugged in, that I used "mkfs.btrfs -f /dev/sdc" to format it and then copy and read some files to it. The next day, after I plugged it in, it wouldn't recognize the btrfs volume.