NVMe Express基础规范2.0解读
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"NVM Express (NVMe) Base Specification 2.0"
NVM Express (NVMe) 是一种高速接口标准，旨在优化主机系统与非易失性存储子系统之间的通信，尤其是针对固态硬盘（SSD）设计。NVMe接口能够通过多种传输方式如PCI Express、Ethernet、InfiniBand和Fibre Channel来实现，适用于各种存储解决方案。这份文档详细定义了NVMe的基础规范，而特定传输方式如Fibre Channel的NVMe绑定规范则在独立的文档中进行描述，如INCITS 556 Fibre Channel - Non-Volatile Memory Express - 2 (FC-NVMe-2)。
NVMe Base Specification 2.0是在2021年5月13日发布的，它整合了之前的1.4版本，以及多个工程变更通知（ECN）和技术提案（TP）。这些ECN和TP涉及NVMe over Fabrics的扩展，对协议进行了多方面的增强和改进。用户可以访问NVM Express组织的官方网站获取该规格书的最新版本及修订详情。
本规范包含了一系列免责声明和法律条款，明确指出该文档是NVM Express, Inc.及其继承者和受让人的专有财产。对于非NVM Express, Inc.的用户，使用此规范需要遵守特定的使用条款。
NVMe规范的主要目标是减少I/O延迟，提高存储系统的性能，同时简化软件堆栈。它引入了一种基于队列的模型，允许并发处理大量I/O请求，提高了系统吞吐量。此外，NVMe还提供了丰富的错误报告机制、服务质量（QoS）控制和安全特性，以满足数据中心和企业级存储的需求。
在NVMe 2.0版本中，可能包括了如下关键更新：
1. 性能提升：可能增加了新的命令集和优化，以进一步提高读写速度和响应时间。
2. 扩展的错误处理：可能增强了错误恢复机制，使得系统更健壮。
3. NVMe over Fabrics：可能增强了网络环境下的支持，包括Fibre Channel和其他传输协议的集成。
4. 安全性增强：可能加入了新的加密和认证机制，以保护数据的安全。
5. QoS改进：可能增加了对不同工作负载和应用的细粒度服务质量控制。
6. 功耗管理：可能优化了低功耗模式和电源效率。
具体的技术细节和更改内容，用户需参考完整的NVMe Base Specification 2.0文档以获取详细信息。由于NVM Express的不断发展，每个新版本都会带来性能、功能和兼容性的提升，使得NVMe成为高性能存储系统的首选接口标准。
NVM Express
®
Base Specification, revision 2.0
4
1.4.1.4 optional
A keyword that describes features that are not required by this specification. However, if any optional
feature defined by the specification is implemented, the feature shall be implemented in the way defined by
the specification.
1.4.1.5 R
“R” is used as an abbreviation for “reserved” when the figure or table does not provide sufficient space for
the full word “reserved”.
1.4.1.6 reserved
A keyword referring to bits, bytes, words, fields, and opcode values that are set-aside for future
standardization. Their use and interpretation may be specified by future extensions to this or other
specifications. A reserved bit, byte, word, field, property, or register shall be cleared to 0h, or in accordance
with a future extension to this specification. The recipient of a command or a register write is not required
to check reserved bits, bytes, words, or fields. Receipt of reserved coded values in defined fields in
commands shall be reported as an error. Writing a reserved coded value into a controller property field
produces undefined results.
1.4.1.7 shall
A keyword indicating a mandatory requirement. Designers are required to implement all such mandatory
requirements to ensure interoperability with other products that conform to the specification.
1.4.1.8 should
A keyword indicating flexibility of choice with a strongly preferred alternative. Equivalent to the phrase “it is
recommended”.
Numerical Descriptions
A 0’s based value is a numbering scheme in which the number 0h represents a value of 1h, 1h represents
2h, 2h represents 3h, etc. In this numbering scheme, there is no method to represent the value of 0h.
Values in this specification are 1-based (i.e., the number 1h represents a value of 1h, 2h represents 2h,
etc.) unless otherwise specified.
Size values are shown in binary units or decimal units. The symbols used to represent these values are as
shown in Figure 2.
Figure 2: Decimal and Binary Units
Decimal
Binary
Symbol
Power
(base-10)
Symbol
Power
(base-2)
kilo / k
10
3
kibi / Ki
2
10
mega / M
10
6
mebi / Mi
2
20
giga / G
10
9
gibi / Gi
2
30
tera / T
10
12
tebi / Ti
2
40
peta / P
10
15
pebi / Pi
2
50
exa / E
10
18
exbi / Ei
2
60
zetta / Z
10
21
zebi / Zi
2
70
yotta / Y
10
24
yobi / Yi
2
80
The ^ operator is used to denote the power to which that number, symbol, or expression is to be raised.
Some parameters are defined as an ASCII string. ASCII strings shall contain only code values 20h through
7Eh. For the string “Copyright”, the character “C” is the first byte, the character “o” is the second byte, etc.
The string is left justified and shall be padded with spaces (ASCII character 20h) to the right if necessary.
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