Re: [PATCH v1 0/7] Add a mtd raid layer

[Dongsheng Yang <yangds.fnst@cn.fujitsu.com>]

Adding Boris...

Hi Boris,
	I found you are working on the problem of
data lose in MLC, there is another idea to protect
the our data, by raid5. What do you think?

https://en.wikipedia.org/wiki/Standard_RAID_levels#RAID_5

Yang

On 12/01/2015 06:52 PM, Dongsheng Yang wrote:
> Hi guys,
> 	I am here to release v1 of the mtd raid layer. It's a layer
> shown as below:
>
> ---------      -------------
> |  ubi  |      |  mtdchar  |
> ---------      -------------
>     |                |
>     v                v
> ----------------------------
> |        MTD RAID          |    <----- a new layer here (drivers/mtd/mtd_raid/*)
> ----------------------------
>             |
>             v
>     ----------------
>     |   mtd driver |
>     ----------------
>
> Of course, that's optional.
>
> There are two ways to use mtd raid.
> (1). For multi-chips driver:
>
> 	   /dev/mtd0
> |--------------------------------|
> |  ----------------------------  |
> |  |        MTD RAID          |  |
> |  ----------------------------  |
> |      |             |           |
> |      v             v           |
> |  -----------   -----------     |
> |  | mtd_info|   | mtd_info|     |
> |  -----------   -----------     |
> |--------------------------------|
>
> When a driver have multiple chips, we can use mtd raid framework to build
> them into a raid array and expose a mtd device. There are some drivers
> are using mtd_concat, we can do the same thing with mtd_single. At the same
> time, mtd raid provides more choices to them, such as raid0 or raid1.
>
> (2). For user:
>
>             /dev/mtd2
> |--------------------------------|
> |  ----------------------------  |
> |  |        MTD RAID          |  |
> |  ----------------------------  |
> |      |             |           |
> |      v             v           |
> |  -----------   -----------     |
> |  |/dev/mtd0|   |/dev/mtd1|     |
> |  -----------   -----------     |
> |--------------------------------|
>
> we have a user tool for mtd raid, and user can use it to build raid array.
>
> Example:
> 	# mtd_raid create --level=0 /dev/mtd0 /dev/mtd1 /dev/mtd2 /dev/mtd3
> 	# mtdinfo /dev/mtd4
> 	mtd4
> 	Name:                           mtdraid0-1
> 	Type:                           nand
> 	Eraseblock size:                65536 bytes, 64.0 KiB
> 	Amount of eraseblocks:          8192 (536870912 bytes, 512.0 MiB)
> 	Minimum input/output unit size: 512 bytes
> 	Sub-page size:                  256 bytes
> 	OOB size:                       16 bytes
> 	Character device major/minor:   90:8
> 	Bad blocks are allowed:         true
> 	Device is writable:             true
>
> There are 4 mtd devices simulated by nandsim, then we create a raid0 with
> them.
> ---------------------------------------------------------------------------
> | device| size |  throughput (dd if=/dev/mtdX of=/dev/null bs=1M count=10)|
> |--------------------------------------------------------------------------
> | mtd0  | 128M |  14.0 MB/s						  |
> |--------------------------------------------------------------------------
> | mtd1  | 128M |  14.0 MB/s						  |
> |--------------------------------------------------------------------------
> | mtd2  | 128M |  14.0 MB/s						  |
> |--------------------------------------------------------------------------
> | mtd3  | 128M |  14.0 MB/s						  |
> |--------------------------------------------------------------------------
> | mtd4  | 512M |  51.1 MB/s						  |
> ---------------------------------------------------------------------------
>
> Also we can use raid1 to get a mirror for robustness.
>
> TODO:
> 	In this framework, we can implement more raid levels. The most useful
> one I think is raid5/6, which would do a parity and fixup work in reading. That's
> important for MLC or TLC. Raid-level is refered to:
>
> https://en.wikipedia.org/wiki/Standard_RAID_levels
>
>
> Code:
> 	kernel:  https://github.com/yangdongsheng/linux  mtd_raid_v1
> 	user  :  https://github.com/yangdongsheng/mtd-utils mtd_raid_v1
>
> Thanx
> Yang
>
> Dongsheng Yang (7):
>    mtd: nandsim: remove the abuse of reference to globle variable.
>    mtd: nansim: add support of multi devices.
>    mtd: mtd_raid: Init a new layer of MTD RAID
>    mtd: mtd_raid: introduce raid single implementation
>    mtd: mtd_raid: introduce raid0 implementation
>    mtd: mtd_raid: introduce raid1 implementation
>    mtd: mtd_raid: implement ioctl for mtd raid
>
>   Documentation/ioctl/ioctl-number.txt |    1 +
>   drivers/mtd/Kconfig                  |    2 +
>   drivers/mtd/Makefile                 |    1 +
>   drivers/mtd/mtd_raid/Kconfig         |   12 +
>   drivers/mtd/mtd_raid/Makefile        |    3 +
>   drivers/mtd/mtd_raid/core.c          | 1000 ++++++++++++++++++++++++++++++++++
>   drivers/mtd/mtd_raid/ioctl.c         |  137 +++++
>   drivers/mtd/mtd_raid/mtd_raid.h      |  264 +++++++++
>   drivers/mtd/mtd_raid/raid0.c         |  136 +++++
>   drivers/mtd/mtd_raid/raid1.c         |  156 ++++++
>   drivers/mtd/mtd_raid/raid_io.c       |  449 +++++++++++++++
>   drivers/mtd/mtd_raid/raid_single.c   |  156 ++++++
>   drivers/mtd/nand/nandsim.c           |  312 ++++++-----
>   include/uapi/mtd/mtd-raid-user.h     |   33 ++
>   14 files changed, 2518 insertions(+), 144 deletions(-)
>   create mode 100644 drivers/mtd/mtd_raid/Kconfig
>   create mode 100644 drivers/mtd/mtd_raid/Makefile
>   create mode 100644 drivers/mtd/mtd_raid/core.c
>   create mode 100644 drivers/mtd/mtd_raid/ioctl.c
>   create mode 100644 drivers/mtd/mtd_raid/mtd_raid.h
>   create mode 100644 drivers/mtd/mtd_raid/raid0.c
>   create mode 100644 drivers/mtd/mtd_raid/raid1.c
>   create mode 100644 drivers/mtd/mtd_raid/raid_io.c
>   create mode 100644 drivers/mtd/mtd_raid/raid_single.c
>   create mode 100644 include/uapi/mtd/mtd-raid-user.h
>