Hello,
I'm new to using bcache and am having difficulty assembling and
mounting the /dev/bcache* devices after their initial creation, at
which time I can mount them.
My goal to to have the root file system as as bcache device. Currently
booting fails as it can't find the root device, which makes sense
given I'm unable to create and mount it from a live environment as
well - although agagin I can mount it fine at time of creation.
Following is the process I am using. I'd really love to get this
working and would appreciate any tips on where I'm going wrong.
Thanks in advance!
Pete
== Initial Config ==
Installed Suse 13.1 using normal Suse installer, with /boot, / and
swap. / is btrfs and LVM.
Booted to Ubuntu 13.10 live CD, installed bcache-tools and blocks from
ppa:g2p/storage
Used blocks to convert /dev/mapper/system-root to bcache
Run make-bache on /dev/mapper/system-root, and /dev/sdb (the SSD) and
joined using th cset ID provided. This appears to have succeeded, and
after which I was able to mount /dev/bcache1 and the cache (per stats
is /sys) was working correctly. All appeared good.
However, after rebooting I am unable to mount it again as I am never
able to get the /dev/bcache* devices to appear again.
== Subsequent reboot, no /dev/bcache* devices ==
Here is what I see on the subsequent reboot from Ubuntu 13.10 Live CD:
No /sys/fs/bcache on boot:
root@ubuntu:~# ls /sys/fs/
btrfs/ cgroup/ ecryptfs/ ext4/ fuse/ pstore/
Add bcahce tools (and blocks):
apt-add-repository ppa:g2p/storage
apt-get update
apt-get install bcache-tools python3-blocks
Attempting to make-bcache again results in bcache device appearing in /sys/fs:
root@ubuntu:~# make-bcache -C /dev/sdb
Already a bcache device on /dev/sdb, overwrite with --wipe-bcache
root@ubuntu:~# ls /sys/fs/
bcache/ btrfs/ cgroup/ ecryptfs/ ext4/ fuse/ pstore/
Register the devices:
root@ubuntu:~# echo /dev/mapper/system-root > /sys/fs/bcache/register
root@ubuntu:~# echo /dev/sdb > /sys/fs/bcache/register
bash: echo: write error: Invalid argument
Perhaps /dev/sdb alredy registered from failed make-bcache above?
root@ubuntu:~# dmesg | tail
[ 559.438930] bcache: register_bcache() error opening /dev/sdb:
device already registered
Examine backing and cache devices superblocks:
root@ubuntu:~# bcache-super-show /dev/mapper/system-root
sb.magic ok
sb.first_sector 8 [match]
sb.csum 815BCC6A0F4B43B6 [match]
sb.version 4 [backing device]
dev.label (empty)
dev.uuid fef7635a-562d-4493-bc9a-eb56eca00609
dev.sectors_per_block 1
dev.sectors_per_bucket 1024
dev.data.first_sector 8192
dev.data.cache_mode 1 [writeback]
dev.data.cache_state 1 [clean]
cset.uuid 00000000-0000-0000-0000-000000000000
root@ubuntu:~# bcache-super-show /dev/sdb
sb.magic ok
sb.first_sector 8 [match]
sb.csum 7E3113141FAB5928 [match]
sb.version 3 [cache device]
dev.label (empty)
dev.uuid 897e3a51-4e38-455c-8989-efffcb707be4
dev.sectors_per_block 1
dev.sectors_per_bucket 1024
dev.cache.first_sector 1024
dev.cache.cache_sectors 234439680
dev.cache.total_sectors 234440704
dev.cache.ordered yes
dev.cache.discard no
dev.cache.pos 0
dev.cache.replacement 0 [lru]
cset.uuid 01f294ff-6898-46b1-9c39-dcba3df35a8c
root@ubuntu:~# cat /sys/block/sdb/bcache/
block_size clear_stats metadata_written
written
btree_written discard nbuckets
bucket_size freelist_percent priority_stats
cache_replacement_policy io_errors set/
root@ubuntu:~# ls /sys/fs/bcache/
01f294ff-6898-46b1-9c39-dcba3df35a8c/ register
register_quiet
root@ubuntu:~# ls /sys/fs/bcache/01f294ff-6898-46b1-9c39-dcba3df35a8c/
average_key_size congested_write_threshold_us stats_five_minute/
block_size dirty_data stats_hour/
btree_cache_size flash_vol_create stats_total/
bucket_size internal/ stop
cache0/ io_error_halflife synchronous
cache_available_percent io_error_limit tree_depth
clear_stats journal_delay_ms unregister
congested root_usage_percent
congested_read_threshold_us stats_day/
Although cache0 shows above is /sys/fs/bcache, there still is no /dev/bcache0:
root@ubuntu:~# mount /dev/b
block/ bsg/ btrfs-control bus/
Try to rejoin? Nope.
root@ubuntu:~# blocks to-bcache /dev/mapper/system-root --join
01f294ff-6898-46b1-9c39-dcba3df35a8c
Device /dev/mapper/system-root already has a bcache super block.
What do I have to do to get /dev/bcache* devices to show again and be
mountable? Hopefully once I figure out manual mounting I can then get
it to be mountable as the root file system by grub2 during.
Thank you again for any help.
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