Copyright (C) 2009-2014, HGST, Inc.

I. Introduction
===============

I.1. Overview
-------------

libzbc is a simple library providing functions for manipulating disks
supporting the Zoned Block Command (ZBC) and Zoned-device ATA command set
(ZAC) disks.  libzbc implemention is compliant with the latest drafts of
the ZBC and ZAC standards defined by INCITS technical committee T10 and
T13 (respectively).

In addition to supporting ZBC and ZAC disks, libzbc also implements an
emulation mode allowing emulating the behavior of a host-managed zoned
disks using a regular file or a raw standard block device as backing
storage.

Several example applications using libzbc are available under the tools
directory.

I.2. Standards Versions Supported
---------------------------------

The "master" code branch provides libzbc v4.0.0 which supports the ZBC
and ZAC standard draft Rev 04.

Support for the older draft standards revision 2 is available as a the
pre-release v2.0.0 (see https://github.com/hgst/libzbc/releases).

Both the ZBC and ZAC standards are still on-going work. However, as this
work is now nearing completion, changes to the command set and command
interface are unlikely in the final public release of the standards.
Nevertheless, any change being incorporated in the final standard
release will be incorporated into libzbc as a new version.

I.3. License
------------

libzbc is distributed under the terms of the of the BSD 2-clause license
("Simplified BSD License" or "FreeBSD License"). A copy of this license
with the library copyright can be found in the COPYING.BSD file.

With the exception of the linear key value store (lkvs) tool, all example
applications under the tools directory are distributed under the terms of
the GNU Lesser General Public License version 3, or any later version. A
copy of version 3 this license can be found in the COPYING.LESSER file.

The lkvs tool is distributed under the terms of the of the GNU General
Public License version 3, or any later version. A copy of version 3 of
this license can be found in the COPYING.GPL file.

libzbc and all its example applications are distributed "as is,"
without technical support, and WITHOUT ANY WARRANTY, without even the
implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
Along with libzbc, you should have received a copy of the BSD 2-clause
license, GNU General Public License and og the GNU Lesser General Public
License. If not, please see <http://opensource.org/licenses/BSD-2-Clause>
and <http://www.gnu.org/licenses/>.

I.4. Contact and Bug Reports
----------------------------

Please contact Damien Le Moal (damien.lemoal@hgst.com) and
Adam Manzanares (adam.manzanares@hgst.com) to report problems.

II. Compilation and installation
================================

II.1. Requiremensts
-------------------

The compilation of libzbc requires that the autoconf, GTK3 and GTK3
development packages be installed on the target host. The GTK3 packages
are only necessary for the gzbc GUI example application.  If this
application is not compiled, installing the GTK3 and GTK3 developemnt
packages is not necessary.

II.2. Compilation
-----------------

To compile the library and all example applications, execute the
following commands.

> sh ./autogen.sh
> ./configure
> make

II.3. Installation
------------------

To install the library and all example applications, as root, execute
the following command.

> make install

The library files are installed in /usr/lib.  The library header files
are installed in /usr/include/libzbc The executable files for the example
applications are installed in /usr/bin.

II.4. Compilation for device tests
----------------------------------

The test directory contains several test programs and scripts allowing 
testing the compatibility of libzbc with a particular device. That is,
testing if a device follows the same standard as currently supported by
libzbc (see section I.2).

The compilation of these test programs is disabled by default. To compile
the test programs, libzbc must be configured as follows.

> sh ./autogen.sh
> ./configure --with-test
> make

And as root,

> make install

This last command does not copy the test programs and scripts anywhere.
All defined tests can be executed directly form the test directory by
executing the zbc_test.sh script.

> cd test
> sudo ./zbc_test.sh /dev/<SG node>

Each test executed outputs a log file in the test/log directory. These
files can be consulted in case of failed test to identify the reason
for the test failure.


III. Usage
==========

III.1 Kernel Version
--------------------

libzbc functions operate using device handles which are obtained by
executing the zbc_open function. This function argument can be a regular
file, a block device file or an SG node device file (/dev/sg<x>).

As of kernel version 4.3, a host-managed SMR device can only be accessed
using its SG nodes. For SATA host-managed SMR devices, device signature
support by the kernel is required for the device SG nodes to exist.

Linux kernel introduced support for ZBC device type with version 3.17. Any
kernel with version 3.17 and above will thus recognize SAS ZBC devices
and create an SG node for these disks, but will not create a regular
block device (such as /dev/sd<y>).

The device signature of SATA ZAC disks is not recognized by kernels
before 3.19. For these kernels, no SG device node is created, resulting
in the impossibility to access ZAC disks.  To enable ZAC device signature
handling for kernels between version 3.17 and 3.19, the following patches
must be used.

https://git.kernel.org/cgit/linux/kernel/git/hare/scsi-devel.git/commit/?h=zac.v2&id=ec07b9a8b168499c6009bf5bfe925a0a10b49729
https://git.kernel.org/cgit/linux/kernel/git/hare/scsi-devel.git/commit/?h=zac.v2&id=02582e1667f05b0c64f2998877216e395e7fda52
https://git.kernel.org/cgit/linux/kernel/git/hare/scsi-devel.git/commit/?h=zac.v2&id=70eb02d6eca2c0706b388a3971f9e156bac092d7

For host-aware devices, the kernel will create both a block device file
and an SG device node. Both can be used to access and control the device
zones information.

Regular files and legacy disk block device files can be used to operate
libzbc in emulation mode. In the latter case, emulation mode will be
enabled only and only if the device is recognized as a regular non-SMR
block device.

III.2 Library Functions
-----------------------

libzbc exports the following functions.

+------------------------------+------------------------------------+
| Function                     | Description                        |
+==============================+====================================+
| zbc_device_is_smr            | Test if a device is a physical ZBC |
|                              | or ZAC device (excludes emulation) |
+------------------------------+------------------------------------+
| zbc_open                     | Open a ZBC device                  |
+------------------------------+------------------------------------+
| zbc_close                    | Close a ZBC device                 |
+------------------------------+------------------------------------+
| zbc_get_device_info          | Get sector and size information    |
+------------------------------+------------------------------------+
| zbc_report_zones             | Get zone information               |
+------------------------------+------------------------------------+
| zbc_report_nr_zones          | Get the number of zones            |
+------------------------------+------------------------------------+
| zbc_list_zones               | Get device zone information        |
+------------------------------+------------------------------------+
| zbc_open_zones               | Explicitely open a zone            |
+------------------------------+------------------------------------+
| zbc_close_zones              | Close an open zone                 |
+------------------------------+------------------------------------+
| zbc_finish_zones             | Finish a zone                      |
+------------------------------+------------------------------------+
| zbc_reset_write_pointer      | Reset a zone write pointer         |
+------------------------------+------------------------------------+
| zbc_pread                    | Read data from a zone              |
+------------------------------+------------------------------------+
| zbc_pwrite                   | Write data to a zone               |
+------------------------------+------------------------------------+
| zbc_write                    | Write data to a sequential zone    |
+------------------------------+------------------------------------+
| zbc_flush                    | Flush data to disk                 |
+------------------------------+------------------------------------+

The current implementation of these functions is NOT thread safe. In
particular, concurrent write operations by multiple threads to the
same zone may result in write errors without write ordering control
by the application.

Additionally, the following functions are also provided to facilitate
application development and tests.

+------------------------+------------------------------------------+
| Function               | Description                              |
+==============================+====================================+
| zbc_set_log_level      | Set log level of the library functions   |
+------------------------+------------------------------------------+
| zbc_disk_type_str      | Get a string description of a disk type  |
+------------------------+------------------------------------------+
| zbc_disk_model_str     | Get a string description of a disk model |
+------------------------+------------------------------------------+
| zbc_zone_type_str      | Get a string description of a zone type  |
+------------------------+------------------------------------------+
| zbc_zone_condition_str | Get a string description of a zone state |
+------------------------+------------------------------------------+

More detailed information on these functions is available through the
comments in the file include/libzbc/zbc.h.


III.3 Native Mode Operation
---------------------------

The standard Linux kernel does not create a block device file for
host-managed ZBC and ZAC disks.  As a result, these devices are only
accessible through their associated SG node (/dev/sgx device file).

Opening a native ZBC or ZAC host managed disk with libzbc thus needs
to be done by specifying the device SG node. Further accesses (report
zones, reset zone write pointer, etc) can then proceed using the device
handle provided by the zbc_open function.

For host-aware devices, the device SG node file or block device file
can both be used to obtain a device handle.

III.4 Emulation Mode Operation
------------------------------

libzbc can emulate host-managed disks operation using a regular
file or a legacy non-SMR standard block device file (regular disk
or loopback device). The use of the library in such case is identical
to the native mode case, assuming that the emulated device is first
configured by executing the zbc_set_zones tool (see next section).


IV. Example Applications
========================

Under the tools directory, several simple applications are available
as examples.  These appliations are as follows.

IV.1. gzbc (tools/gui)
----------------------

gzbc provides a graphical user interface showing zone information of a
zoned device.  It also displays the write status (write pointer position)
of zones graphically using color coding (red for written space and green
for unwritten space). Some operations on zones can also be executed
directly from the interface (reset zone write pointer, open zone, close
zone, etc).

IV.2. zbc_report_zones (tools/report_zones/)
--------------------------------------------

This application illustrates the use of the zone reporting functions
(zbc_report_zones, zbc_report_nr_zones, zbc_list_zones).  It obtains
the zone information of a device and displays it in readable form on
the standard output.

IV.3. zbc_open_zone (tools/open_zone/)
--------------------------------------------------

This application illustrates the use of the zbc_open_zone
function allowing opening a zone.

IV.4. zbc_close_zone (tools/close_zone/)
--------------------------------------------------

This application illustrates the use of the zbc_close_zone
function allowing closing a zone.

IV.5. zbc_finish_zone (tools/finish_zone/)
--------------------------------------------------

This application illustrates the use of the zbc_finish_zone
function allowing finishing a zone.

IV.6. zbc_reset_write_ptr (tools/reset_write_ptr/)
--------------------------------------------------

This application illustrates the use of the zbc_reset_write_pointer
function allowing resetting the write pointer of a zone to the start
LBA of the zone.

IV.7. zbc_read_zone (tools/read_zone/)
--------------------------------------

This application reads data from a zone, up to the zone write pointer
location and either send the read data to the standard output or copy
the data to a regular file. It implementation uses the function zbc_pread.

IV.8. zbc_write_zone (tools/write_zone/)
----------------------------------------

This application illustrates the use of the zbc_pwrite function which
write data to a zone at the zone write pointer location.

IV.9. zbc_set_zones (tools/set_zones/)
--------------------------------------

This application can be used to initialize the ZBC emulation mode for
a regular file or a raw standard block device.

IV.10. zbc_set_write_ptr (tools/set_write_ptr/)
----------------------------------------------

This application can be used to set the write pointer of a zone of an
emulated ZBC device to any LBA value (within the range of the specified
zone). It is intended for testing purposes only and is not valid for
native ZBC devices.

IV.11. zbc_info (tools/info/)
-----------------------------

This application tests if a device file points to a physical SMR device
supporting either ZBC or ZAC. This excludes the emulation mode implemented
by libzbc on top of regular files or regular block devices.
If the device is identified as SMR, some information about the device are
displayed (device type, capacity, sector size, etc).

IV.12. lkvs (tools/lkvs/)
------------------------

### Purpose

ZBC drives have three types of zones: conventional, sequential preferred,
and sequential only. This project aims to create a key/value store on
top of a drive that contains seqential only zones exclusively. I.e. all writes
to the drive must be linear within the LBA space of one zone.

This work is intended to be a demonstration of how to build systems software on
top of a ZBC drive. This is not a full featured key/value store and we do not 
intend it to be so. 

The main limitations of the current design is that we require all 
of the metadata for the KV store to fit into main memory and there is no garbage 
collection built into LKVS. Therfor, updates to an existing key are not 
supported. 

If you want to build the python or java bindings please pass the option
of --with-pybind or --with-javabind to the configure script, to build the 
corresponding bindings. 

### How To Run LKVS tests

Must be done after make install of libzbc.

```
cd tools/lkvs
sudo make check-local LKVSDEVFILE=/path/to/zbcdevice
```
Also make sure that src/test/zbc_reset.sh is executable.

### How to Build Python or Java bindings

```
cd tools/lkvs
make pybind
make javabind
```

Cleaning the bindings

```
make pybind-clean
make javabind-clean
```

### Using LKVS

#### C++
See src/examples

#### Python 
See src/pybind/example.py

#### Java
See src/javabind/Tester.java

### LKVS Contact Information

Contact: adam.manzanares@hgst.com