Does bcache require a fresh installation?

Question

Because my notebook has a SSD and a HDD, I want use the SSD as cache just like Rapid Storage in windows. I find bcache offers this functionality so I decide to try it.

I got bcache and bcache-tools via git then followed the guide at:

http://evilpiepirate.org/git/linux-bcache.git/tree/Documentation/bcache.txt

Getting started:
You'll need make-bcache from the bcache-tools repository. Both the cache device
and backing device must be formatted before use.
  make-bcache -B /dev/sdb
  make-bcache -C -w2k -b1M -j64 /dev/sdc

Does that mean I have to format the whole HDD to enable the bcache?

Answer 1

Is that means I have to format the whole HDD to enable the bcache?

That's certainly what is suggests, yes. This is fairly common in RAID-like situations. You start by generating a new mapped bcache device and then you format that, instead of the hardware directly.

However, the other RAID-like things (mdadm, dmraid, etc) have documentation that make it quite clear how you create one of these setups and then install on top of it (and have initramfs load the right stuff so you can boot!)

I'm fairly experienced messing around with bizarre filesystem arrangements and kernel modules and even I wouldn't want to touch this. Especially not if I was trying to retrofit it into an existing installation.

I would concentrate on what I've got in front of me. If your SSD is fast and of a moderate size ~10GB+, stick Ubuntu on there and host /home on the spinning rust. That should give you some room for installing things but at some point you might have to move /opt to rust. It may seem complicated now but it's quite easy to split an installation over multiple disks.

If the SSD is tiny (<8GB) and/or slow, it may be worth considering just not using it.