Re: Best way to add caching to a new raid setup.

[Roman Mamedov <rm@romanrm.net>]

On Thu, 27 Aug 2020 21:31:07 -0500
"R. Ramesh" <rramesh@verizon.net> wrote:

> I have two raid6s running on mythbuntu 14.04. The are built on 6 
> enterprise drives. So, no hd issues as of now. Still, I plan to upgrade 
> as it has been a while and the size of the hard drives have become 
> significantly larger (a indication that my disks may be older) I want to 
> build new raid using the 16/14tb drives. Since I am building new raid, I 
> thought I could explore caching options. I see a mention of LVM cache 
> and few other bcache/xyzcache etc.

Once you set up bcache, it cannot be removed. The volume will always stay a
bcache volume, even if you decide to stop using caching. Which feels weird and
potentially troublesome, going through an extra layer (kernel driver) with its
complexity and computational overhead (no matter how small).

On the other hand LVM with caching turned off is just normal LVM, that you'd
likely would have used anyway, for other benefits that it provides.

Also my impression is that LVM has more solid and reliable codebase, but
bcache might provide a somewhat better the performance boost due to caching.

-- 
With respect,
Roman