#2057 Issue closed: Support bcache in ReaR

Labels: enhancement, no-issue-activity

jsmeix opened issue at 2019-02-28 08:18:

Because 'bcache' (ignore case) is nowhere mentioned in ReaR
I assume current ReaR does not support bcache.

Upcoming openSUSE and SUSE Linux Enterprise versions
will have bcache support in YaST and ReaR should be able
to recreate "normally" installed openSUSE and SLES systems.

Accordingly a future ReaR version should support bcache.

For background information about bcache support at SUSE see
https://lizards.opensuse.org/2019/02/27/recap-bcache-in-yast/
that reads (excerpts):

... what is Bcache? It’s a Linux technology that allows
to improve the performance of any big but relative slow
storage device (so-called “backing device” in Bcache terminology)
by using a faster and smaller device (so-called caching device)
to speed up read and write operations. The resulting Bcache device
has then the size of the backing device and (almost) the effective
speed of the caching one.

In other words, you can use one or several solid state drives,
which are typically fast but small and expensive, to act as a cache
for one or several traditional rotational (cheap and big) hard disks…
effectively getting the best of both worlds.

How does it all look in your Linux system?
Let’s explain it with some good old ASCII art:

(slow hard disk) (faster device, SSD)
    /dev/sda          /dev/sdb
      |                   |
[Backing device] [Caching device] <-- Actually, this is a set of
      |                   |           caching devices (Caching Set)
      |_________ _________|
                |
             [Bcache]
          /dev/bcache0

Take into account that the same caching device
(or the same “caching set”, sticking to Bcache terminology)
can be shared by several Bcache devices.

If you are thinking about using Bcache later, it is also possible to setup
all your slow devices as Bcache backing devices without a cache.
Then you can add the caching device(s) at a later point in time.

(slow hard disk)
    /dev/sda   
      |         
[Backing device]
      |
      |__________ __________|
                 |
              [Bcache]
           /dev/bcache0

Last but not least, the Bcache technology allows to create
virtual devices on top of an existing caching set without
an associated backing device. Such a device is known
as Flash-only Bcache and is only useful in some very specific use cases.

                   (faster device, SSD)
                        /dev/sdb
                            |
                    [Caching device]
                            |
      |__________ __________|
                 |
         [Flash-only Bcache]
           /dev/bcache0

github-actions commented at 2020-06-28 01:33:

Stale issue message

[Export of Github issue for rear/rear.]