>
>
> Bad superblocks can't be a good thing and would only cause confusion.
> I'd think that a known bad superblock would be ignored at mount time
> and even by btrfs-find-root, or maybe even replaced like any other kind
> of known bad metadata where good copies are available.
>
> btrfs-show-super -f /dev/sda
> btrfs-show-super -f /dev/sdh
>
>
> Find out what the difference is between good and bad supers.
>
root@castor:~# btrfs-show-super -f /dev/sda
superblock: bytenr=65536, device=/dev/sda
---------------------------------------------------------
csum_type 0 (crc32c)
csum_size 4
csum 0x45278835 [match]
bytenr 65536
flags 0x1
( WRITTEN )
magic _BHRfS_M [match]
fsid 73ed01df-fb2a-4b27-b6fc-12a57da934bd
label
generation 161562
root 5752616386560
sys_array_size 354
chunk_root_generation 156893
root_level 1
chunk_root 20971520
chunk_root_level 1
log_root 0
log_root_transid 0
log_root_level 0
total_bytes 18003557892096
bytes_used 7107627130880
sectorsize 4096
nodesize 16384
leafsize 16384
stripesize 4096
root_dir 6
num_devices 6
compat_flags 0x0
compat_ro_flags 0x0
incompat_flags 0xe1
( MIXED_BACKREF |
BIG_METADATA |
EXTENDED_IREF |
RAID56 )
cache_generation 161562
uuid_tree_generation 161562
dev_item.uuid 08c50aa9-c2dd-43b7-a631-6dfdc7d69ea4
dev_item.fsid 73ed01df-fb2a-4b27-b6fc-12a57da934bd [match]
dev_item.type 0
dev_item.total_bytes 3000592982016
dev_item.bytes_used 1800957198336
dev_item.io_align 4096
dev_item.io_width 4096
dev_item.sector_size 4096
dev_item.devid 1
dev_item.dev_group 0
dev_item.seek_speed 0
dev_item.bandwidth 0
dev_item.generation 0
sys_chunk_array[2048]:
item 0 key (FIRST_CHUNK_TREE CHUNK_ITEM 0)
chunk length 4194304 owner 2 stripe_len 65536
type SYSTEM num_stripes 1
stripe 0 devid 1 offset 0
dev uuid: 08c50aa9-c2dd-43b7-a631-6dfdc7d69ea4
item 1 key (FIRST_CHUNK_TREE CHUNK_ITEM 20971520)
chunk length 11010048 owner 2 stripe_len 65536
type SYSTEM|RAID6 num_stripes 6
stripe 0 devid 6 offset 1048576
dev uuid: 390a1fd8-cc6c-40e7-b0b5-88ca7dcbcc32
stripe 1 devid 5 offset 1048576
dev uuid: 2df974c5-9dde-4062-81e9-c6eeee13db62
stripe 2 devid 4 offset 1048576
dev uuid: dce3d159-721d-4859-9955-37a03769bb0d
stripe 3 devid 3 offset 1048576
dev uuid: 6f7142db-824c-4791-a5b2-d6ce11c81c8f
stripe 4 devid 2 offset 1048576
dev uuid: dc8760f1-2c54-4134-a9a7-a0ac2b7a9f1c
stripe 5 devid 1 offset 20971520
dev uuid: 08c50aa9-c2dd-43b7-a631-6dfdc7d69ea4
backup_roots[4]:
backup 0:
backup_tree_root: 5752437456896 gen: 161561 level: 1
backup_chunk_root: 20971520 gen: 156893 level: 1
backup_extent_root: 5752385224704 gen: 161561 level: 2
backup_fs_root: 124387328 gen: 74008 level: 0
backup_dev_root: 5752437587968 gen: 161561 level: 1
backup_csum_root: 5752389615616 gen: 161561 level: 3
backup_total_bytes: 18003557892096
backup_bytes_used: 7112579833856
backup_num_devices: 6
backup 1:
backup_tree_root: 5752616386560 gen: 161562 level: 1
backup_chunk_root: 20971520 gen: 156893 level: 1
backup_extent_root: 5752649416704 gen: 161563 level: 2
backup_fs_root: 124387328 gen: 74008 level: 0
backup_dev_root: 5752616501248 gen: 161562 level: 1
backup_csum_root: 5752650203136 gen: 161563 level: 3
backup_total_bytes: 18003557892096
backup_bytes_used: 7107602407424
backup_num_devices: 6
backup 2:
backup_tree_root: 5752112103424 gen: 161559 level: 1
backup_chunk_root: 20971520 gen: 156893 level: 1
backup_extent_root: 5752207409152 gen: 161560 level: 2
backup_fs_root: 124387328 gen: 74008 level: 0
backup_dev_root: 5752113463296 gen: 161559 level: 1
backup_csum_root: 5752205492224 gen: 161560 level: 3
backup_total_bytes: 18003557892096
backup_bytes_used: 7112514002944
backup_num_devices: 6
backup 3:
backup_tree_root: 5752298307584 gen: 161560 level: 1
backup_chunk_root: 20971520 gen: 156893 level: 1
backup_extent_root: 5752385224704 gen: 161561 level: 2
backup_fs_root: 124387328 gen: 74008 level: 0
backup_dev_root: 5752299978752 gen: 161560 level: 1
backup_csum_root: 5752389615616 gen: 161561 level: 3
backup_total_bytes: 18003557892096
backup_bytes_used: 7112542425088
backup_num_devices: 6
root@castor:~# btrfs-show-super -f /dev/sdh
superblock: bytenr=65536, device=/dev/sdh
---------------------------------------------------------
csum_type 0 (crc32c)
csum_size 4
csum 0x0f7dfe09 [match]
bytenr 65536
flags 0x1
( WRITTEN )
magic _BHRfS_M [match]
fsid 73ed01df-fb2a-4b27-b6fc-12a57da934bd
label
generation 161474
root 4844272943104
sys_array_size 354
chunk_root_generation 156893
root_level 1
chunk_root 20971520
chunk_root_level 1
log_root 0
log_root_transid 0
log_root_level 0
total_bytes 18003557892096
bytes_used 7110395990016
sectorsize 4096
nodesize 16384
leafsize 16384
stripesize 4096
root_dir 6
num_devices 6
compat_flags 0x0
compat_ro_flags 0x0
incompat_flags 0xe1
( MIXED_BACKREF |
BIG_METADATA |
EXTENDED_IREF |
RAID56 )
cache_generation 161474
uuid_tree_generation 161474
dev_item.uuid dc8760f1-2c54-4134-a9a7-a0ac2b7a9f1c
dev_item.fsid 73ed01df-fb2a-4b27-b6fc-12a57da934bd [match]
dev_item.type 0
dev_item.total_bytes 3000592982016
dev_item.bytes_used 1800936226816
dev_item.io_align 4096
dev_item.io_width 4096
dev_item.sector_size 4096
dev_item.devid 2
dev_item.dev_group 0
dev_item.seek_speed 0
dev_item.bandwidth 0
dev_item.generation 0
sys_chunk_array[2048]:
item 0 key (FIRST_CHUNK_TREE CHUNK_ITEM 0)
chunk length 4194304 owner 2 stripe_len 65536
type SYSTEM num_stripes 1
stripe 0 devid 1 offset 0
dev uuid: 08c50aa9-c2dd-43b7-a631-6dfdc7d69ea4
item 1 key (FIRST_CHUNK_TREE CHUNK_ITEM 20971520)
chunk length 11010048 owner 2 stripe_len 65536
type SYSTEM|RAID6 num_stripes 6
stripe 0 devid 6 offset 1048576
dev uuid: 390a1fd8-cc6c-40e7-b0b5-88ca7dcbcc32
stripe 1 devid 5 offset 1048576
dev uuid: 2df974c5-9dde-4062-81e9-c6eeee13db62
stripe 2 devid 4 offset 1048576
dev uuid: dce3d159-721d-4859-9955-37a03769bb0d
stripe 3 devid 3 offset 1048576
dev uuid: 6f7142db-824c-4791-a5b2-d6ce11c81c8f
stripe 4 devid 2 offset 1048576
dev uuid: dc8760f1-2c54-4134-a9a7-a0ac2b7a9f1c
stripe 5 devid 1 offset 20971520
dev uuid: 08c50aa9-c2dd-43b7-a631-6dfdc7d69ea4
backup_roots[4]:
backup 0:
backup_tree_root: 4844253364224 gen: 161473 level: 1
backup_chunk_root: 20971520 gen: 156893 level: 1
backup_extent_root: 4844248121344 gen: 161473 level: 2
backup_fs_root: 124387328 gen: 74008 level: 0
backup_dev_root: 1411186688 gen: 156893 level: 1
backup_csum_root: 4844247793664 gen: 161473 level: 3
backup_total_bytes: 18003557892096
backup_bytes_used: 7110380077056
backup_num_devices: 6
backup 1:
backup_tree_root: 4844272943104 gen: 161474 level: 1
backup_chunk_root: 20971520 gen: 156893 level: 1
backup_extent_root: 4844268240896 gen: 161474 level: 2
backup_fs_root: 124387328 gen: 74008 level: 0
backup_dev_root: 1411186688 gen: 156893 level: 1
backup_csum_root: 4844254216192 gen: 161474 level: 3
backup_total_bytes: 18003557892096
backup_bytes_used: 7110395990016
backup_num_devices: 6
backup 2:
backup_tree_root: 4844252168192 gen: 161471 level: 1
backup_chunk_root: 20971520 gen: 156893 level: 1
backup_extent_root: 4844242698240 gen: 161471 level: 2
backup_fs_root: 124387328 gen: 74008 level: 0
backup_dev_root: 1411186688 gen: 156893 level: 1
backup_csum_root: 4844241764352 gen: 161471 level: 3
backup_total_bytes: 18003557892096
backup_bytes_used: 7110343888896
backup_num_devices: 6
backup 3:
backup_tree_root: 4844263358464 gen: 161472 level: 1
backup_chunk_root: 20971520 gen: 156893 level: 1
backup_extent_root: 4844261965824 gen: 161472 level: 2
backup_fs_root: 124387328 gen: 74008 level: 0
backup_dev_root: 1411186688 gen: 156893 level: 1
backup_csum_root: 4844261801984 gen: 161472 level: 3
backup_total_bytes: 18003557892096
backup_bytes_used: 7110370037760
backup_num_devices: 6
root@castor:~# btrfs-show-super -f /dev/sda > sda
root@castor:~# btrfs-show-super -f /dev/sdh > sdh
root@castor:~# diff -u sda sdh
--- sda 2016-10-11 11:09:42.853170807 -0500
+++ sdh 2016-10-11 11:09:46.469082028 -0500
@@ -1,16 +1,16 @@
-superblock: bytenr=65536, device=/dev/sda
+superblock: bytenr=65536, device=/dev/sdh
---------------------------------------------------------
csum_type 0 (crc32c)
csum_size 4
-csum 0x45278835 [match]
+csum 0x0f7dfe09 [match]
bytenr 65536
flags 0x1
( WRITTEN )
magic _BHRfS_M [match]
fsid 73ed01df-fb2a-4b27-b6fc-12a57da934bd
label
-generation 161562
-root 5752616386560
+generation 161474
+root 4844272943104
sys_array_size 354
chunk_root_generation 156893
root_level 1
@@ -20,7 +20,7 @@
log_root_transid 0
log_root_level 0
total_bytes 18003557892096
-bytes_used 7107627130880
+bytes_used 7110395990016
sectorsize 4096
nodesize 16384
leafsize 16384
@@ -34,17 +34,17 @@
BIG_METADATA |
EXTENDED_IREF |
RAID56 )
-cache_generation 161562
-uuid_tree_generation 161562
-dev_item.uuid 08c50aa9-c2dd-43b7-a631-6dfdc7d69ea4
+cache_generation 161474
+uuid_tree_generation 161474
+dev_item.uuid dc8760f1-2c54-4134-a9a7-a0ac2b7a9f1c
dev_item.fsid 73ed01df-fb2a-4b27-b6fc-12a57da934bd [match]
dev_item.type 0
dev_item.total_bytes 3000592982016
-dev_item.bytes_used 1800957198336
+dev_item.bytes_used 1800936226816
dev_item.io_align 4096
dev_item.io_width 4096
dev_item.sector_size 4096
-dev_item.devid 1
+dev_item.devid 2
dev_item.dev_group 0
dev_item.seek_speed 0
dev_item.bandwidth 0
@@ -72,47 +72,47 @@
dev uuid: 08c50aa9-c2dd-43b7-a631-6dfdc7d69ea4
backup_roots[4]:
backup 0:
- backup_tree_root: 5752437456896 gen: 161561 level: 1
+ backup_tree_root: 4844253364224 gen: 161473 level: 1
backup_chunk_root: 20971520 gen: 156893 level: 1
- backup_extent_root: 5752385224704 gen: 161561 level: 2
+ backup_extent_root: 4844248121344 gen: 161473 level: 2
backup_fs_root: 124387328 gen: 74008 level: 0
- backup_dev_root: 5752437587968 gen: 161561 level: 1
- backup_csum_root: 5752389615616 gen: 161561 level: 3
+ backup_dev_root: 1411186688 gen: 156893 level: 1
+ backup_csum_root: 4844247793664 gen: 161473 level: 3
backup_total_bytes: 18003557892096
- backup_bytes_used: 7112579833856
+ backup_bytes_used: 7110380077056
backup_num_devices: 6
backup 1:
- backup_tree_root: 5752616386560 gen: 161562 level: 1
+ backup_tree_root: 4844272943104 gen: 161474 level: 1
backup_chunk_root: 20971520 gen: 156893 level: 1
- backup_extent_root: 5752649416704 gen: 161563 level: 2
+ backup_extent_root: 4844268240896 gen: 161474 level: 2
backup_fs_root: 124387328 gen: 74008 level: 0
- backup_dev_root: 5752616501248 gen: 161562 level: 1
- backup_csum_root: 5752650203136 gen: 161563 level: 3
+ backup_dev_root: 1411186688 gen: 156893 level: 1
+ backup_csum_root: 4844254216192 gen: 161474 level: 3
backup_total_bytes: 18003557892096
- backup_bytes_used: 7107602407424
+ backup_bytes_used: 7110395990016
backup_num_devices: 6
backup 2:
- backup_tree_root: 5752112103424 gen: 161559 level: 1
+ backup_tree_root: 4844252168192 gen: 161471 level: 1
backup_chunk_root: 20971520 gen: 156893 level: 1
- backup_extent_root: 5752207409152 gen: 161560 level: 2
+ backup_extent_root: 4844242698240 gen: 161471 level: 2
backup_fs_root: 124387328 gen: 74008 level: 0
- backup_dev_root: 5752113463296 gen: 161559 level: 1
- backup_csum_root: 5752205492224 gen: 161560 level: 3
+ backup_dev_root: 1411186688 gen: 156893 level: 1
+ backup_csum_root: 4844241764352 gen: 161471 level: 3
backup_total_bytes: 18003557892096
- backup_bytes_used: 7112514002944
+ backup_bytes_used: 7110343888896
backup_num_devices: 6
backup 3:
- backup_tree_root: 5752298307584 gen: 161560 level: 1
+ backup_tree_root: 4844263358464 gen: 161472 level: 1
backup_chunk_root: 20971520 gen: 156893 level: 1
- backup_extent_root: 5752385224704 gen: 161561 level: 2
+ backup_extent_root: 4844261965824 gen: 161472 level: 2
backup_fs_root: 124387328 gen: 74008 level: 0
- backup_dev_root: 5752299978752 gen: 161560 level: 1
- backup_csum_root: 5752389615616 gen: 161561 level: 3
+ backup_dev_root: 1411186688 gen: 156893 level: 1
+ backup_csum_root: 4844261801984 gen: 161472 level: 3
backup_total_bytes: 18003557892096
- backup_bytes_used: 7112542425088
+ backup_bytes_used: 7110370037760
backup_num_devices: 6
--
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