[Stgt-devel] Relation between device types & backing store

FUJITA Tomonori fujita.tomonori
Thu Apr 3 09:45:46 CEST 2008

On Wed, 02 Apr 2008 17:13:04 +0300
Erez Zilber <erezz at voltaire.com> wrote:

> We;re trying to understand the relations between devices (mmc, osd, sbc,
> scc & smc) & backing store (bs, bs_aio, bs_mmap & bs_rdrw).

The device modules emulate t10 device types.

Backing store modules define how they access to persistent storage

For example, if sbc uses bs_aio, sbc uses AIO system calls to access
to read from/write to disk. If it uses bs_mmap, it uses mmap system
call. It it uses bs_rdrw, it uses read/write system calls.

Identically, a device module can use all the backing store
modules though there are some exceptions.

> Also, a
> device has the following ops: lu_init, lu_exit & lu_config. What are
> they used for?

They are used for the initialization, exit, and configuration of t10
device types.

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