Arch Linux

miotatsu

Member

Registered: 2013-04-17

Posts: 12

Installing arch with bcache?

I am confused as to how to install arch with bcache. I intend to use my entire HDD for /home, with a partition on my SSD acting as cache. 
Following the typical install procedure and referencing the arch wiki page on bcache, I ran into a problem.

When I boot the install medium, if I `ls /sys/fs` I only see btrfs, cgroup, ext4, and pstore.
Using `arch-chroot` to chroot into my system after mounting `/` and `/boot` (can not mount my hdd as bcache is an unknown filesystem type), I see the same entries in `/sys/fs`. `ls /sys/block` shows dm-0 (?), loop devices 0-7 (?), sda (SSD), sdb (HDD), and sdc (flash drive with install medium).

This is a problem because according to the arch wiki page on bcache I need to write the `cset.uuid` to `/sys/block/bcache0/bcache/attach`.
Furthermore, the bottom of the arch wiki page on bcache says that if `/sys/fs/bcache` does not exist, it means that the kernel booted does not support bcache.

Does that mean that the current stock kernel for Arch Linux is erroneously compiled without bcache support, or am I doing something wrong?
Any help would be greatly appreciated!

byte

Member

From: Düsseldorf (DE)

Registered: 2006-05-01

Posts: 2,046

Re: Installing arch with bcache?

modprobe bcache

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1000

miotatsu

Member

Registered: 2013-04-17

Posts: 12

Re: Installing arch with bcache?

Finally found time to look into this more. `modprobe bcache` got me closer, but I'm still having problems setting this up. After doing `modprobe bcache` I was able to "register" the partition on my SSD with bcache. By the way, do I need to do this chrooted into my partially done install? Trying to register it inside the chroot gave me an error as the filesystem was seen as read-only...

So now in the install medium I try to "attach." `/sys/block/bcache0/bcache` still does not exist for me, but I discovered that `/sys/block/sda/sda4/bcache` does.
However, when I `ls` it, there is no "attach," and when I attempt `echo cset.uuid > /sys/block/sda/sda4/bcache/attach` (where cset.uuid is replaced with the appropriate uuid), I get permission denied (despite being root...)

As always, any help would be greatly appreciated
I apologize for needing a bit of hand-holding here, but I am new to bcache and the arch wiki page on it hasn't been much help to me so far. I might have to update it when I get this working!

Rethil

Member

Registered: 2014-08-21

Posts: 83

Re: Installing arch with bcache?

I'm using lvmcache over bcache so I can't help you in this particular problem, but I would recommend to check out lvmcache - unless there is some drawback about lvm that makes you choose bcache instead ofc.