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Can't enable writeback

DISCUSSION Nick Payne 2 participants 3 messages Aug 17, 2013 bcache (block layer cache)

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Nick Payne

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I've installed kernel 3.10.7 on Ubuntu 13.04 amd64, and bcache-tools from https://launchpad.net/~mighost/+archive/ppa/+build/4767454/+files/bcache-tools_1.0-1ppa1%7Eraring_amd64.deb. I can create a bcache volume and mount and use it without any problems using writethrough (120GB Intel 330 SSD caching a WD 2GB HDD), but when I try to enable writeback:

sudo echo writeback > /sys/block/bcache0/cache_mode

it returns the error

bash: /sys/block/bcache0/cache_mode: No such file or directory

/sys/block/bcache0 exists as a link:

ls -l /sys/block/bc*
lrwxrwxrwx 1 root root 0 Aug 17 15:58 /sys/block/bcache0 ->
../devices/virtual/block/bcache0

Suggestions on how to enable writeback?

Nick Payne

#1 lore raw
Quoted 7 lines

I try to enable writeback:

sudo echo writeback > /sys/block/bcache0/cache_mode

it returns the error

bash: /sys/block/bcache0/cache_mode: No such file or directory

You're confusing bcache0 with bcache0/bcache

echo writeback |sudo tee -a /sys/block/bcache0/bcache/cache_mode

will work.

author
#2 lore raw
Quoted 4 lines · Gabriel de Perthuis
Quoted 4 lines

I try to enable writeback:

sudo echo writeback > /sys/block/bcache0/cache_mode

Quoted 8 lines
Quoted 3 lines

it returns the error

bash: /sys/block/bcache0/cache_mode: No such file or directory

You're confusing bcache0 with bcache0/bcache

echo writeback |sudo tee -a /sys/block/bcache0/bcache/cache_mode

will work.

Thanks, that works. The command I was originally trying to use is what is shown in the documentation at http://evilpiepirate.org/git/linux-bcache.git/tree/Documentation/bcache.txt. It has

    # echo writeback > /sys/block/bcache0/cache_mode

as the command to run.