Ext4 文件系统中大型目录结构的最佳实践

原文： https://elufasys.com/optimizing-space-utilization-for-large-directories-in-ext4-file-systems1

下面是翻译学习笔记

• Table of Contents 目录
  • Introduction 介绍
  • Strategies for Efficient Inode Management in Ext4 File Systems 在 Ext4 文件系统中实现高效 inode 管理的策略
  • Implementing Directory Indexing Techniques in Ext4 for Improved Performance 在 Ext4 中实施目录索引技术以提高性能
  • Best Practices for Large Directory Structures in Ext4 File Systems Ext4 文件系统中大型目录结构的最佳实践
  • Conclusion 结论

1. Introduction 介绍

Optimizing space utilization in large directories within Ext4 file systems is crucial for enhancing system performance and storage efficiency. 优化 Ext4 文件系统中大型目录的空间利用率对于提高系统性能和存储效率至关重要。

划重点：大目录的优化

Ext4, an extended file system for Linux, supports large volumes and files, making it widely used in various computing environments.

Ext4 是 Linux 的扩展文件系统，支持大容量和文件，使其广泛应用于各种计算环境 ext4成为Linux官方的建议默认文件系统

划重点：大目录 ，大文件

As directories grow in size, containing thousands or even millions of files, challenges such as increased lookup times and space wastage can arise.

随着目录大小的增加，包含数千甚至数百万个文件，可能会出现查找时间和空间浪费等挑战

划重点：海量存储场景 查找算法 和数据结构存储

Efficient management of these large directories involves techniques such as indexing, directory hashing, and dynamic inode allocation.

这些大型目录的高效管理涉及索引、目录哈希和动态 inode 分配等技术

These optimizations help in reducing disk space fragmentation, improving file access times, and ensuring scalable and robust directory structures. 这些优化有助于减少磁盘空间碎片，缩短文件访问时间，并确保可扩展且强大的目录结构

Understanding and implementing these strategies is essential for system administrators and developers to maintain optimal performance in systems with extensive data storage requirements.

了解和实施这些策略对于系统管理员和开发人员在具有广泛数据存储要求的系统中保持最佳性能至关重要。

2. Strategies for Efficient Inode Management in Ext4 File Systems

在 Ext4 文件系统中实现高效 inode 管理的策略

划重点：inode 管理的策略是啥？

Optimizing space utilization in large directories within Ext4 file systems is a critical aspect of maintaining system performance and efficiency.

优化 Ext4 文件系统中大型目录的空间利用率是保持系统性能和效率的关键方面。

Ext4, which stands for Fourth Extended Filesystem, is widely used in the Linux environment due to its robustness and scalability.

Ext4 代表第四扩展文件系统，由于其健壮性和可扩展性而广泛用于 Linux 环境

One of the key components in managing Ext4 file systems effectively is efficient inode management. 有效管理 Ext4 文件系统的关键组件之一是高效的 inode 管理。

Inodes play a crucial role as they store essential information about files such as user and group permissions, file size, file type, and pointers to the data blocks.

索引节点起着至关重要的作用，因为它们存储有关文件的基本信息， 例如用户和组权限、文件大小、文件类型以及指向数据块的指针。

划重点：指向数据块的指针？

In large directories, where the number of files and subdirectories can be substantial, inode allocation and management become increasingly complex and can lead to performance degradation if not handled correctly.

在文件和子目录数量可能很大的大型目录中，inode 分配和管理变得越来越复杂，如果处理不当，可能会导致性能下降。

划重点：为什么导致性能下降？我感受不到

The default inode size in Ext4 is 256 bytes, but this can be adjusted during the filesystem creation based on expected usage patterns and directory sizes.

Ext4 中的默认 inode 大小为 256 字节，但可以在创建文件系统时根据预期的使用模式和目录大小进行调整

Increasing the inode size can accommodate more extended attributes, which are used to store additional metadata about files. 增加 inode 大小可以容纳更多扩展属性，这些属性用于存储有关文件的其他元数据

This adjustment, however, consumes more disk space and should be balanced against the actual needs of the system. 但是，此调整会占用更多的磁盘空间，并且应根据系统的实际需求进行平衡。

方案：增加indoe结构大小，需要更多存储空间

Another strategy for optimizing inode management in Ext4 is to utilize the ‘dir_index’ feature.

This feature enables the use of hashed b-trees to manage directory entries instead of the traditional linear directory lists. 在 Ext4 中优化 inode 管理的另一种策略是利用 'dir_index' 功能。此功能允许使用经过哈希处理的 b 树来管理目录条目，而不是传统的线性目录列表

This is particularly beneficial for large directories as it significantly speeds up the search process within the directory by reducing the time complexity from linear to logarithmic. 这对于大型目录特别有用，因为它通过将时间复杂度从线性降低到对数，显著加快了目录中的搜索过程。

划重点：查询大目录下的文件 时间复杂度 从o(n) 降低o(logn)

Enabling dir_index can be done using the ‘tune2fs’ utility, which modifies the filesystem parameters on an existing Ext4 filesystem. 可以使用 'tune2fs' 实用程序启用 dir_index， 该实用程序会修改现有 Ext4 文件系统上的文件系统参数。

划重点:不需要调整代码，只开启参数 开启

In conclusion, managing space utilization in large directories of Ext4 file systems involves a combination of strategic inode sizing, enabling directory indexing, adjusting inode density, utilizing performance-enhancing mount options, and regular filesystem maintenance. By implementing these strategies, system administrators can ensure efficient data management and high performance in large-scale Linux environments.

总之，管理 Ext4 文件系统大型目录中的空间利用率涉及战略性 inode 大小调整、启用目录索引、调整 inode 密度、利用性能增强的挂载选项和定期文件系统维护的组合。通过实施这些策略，系统管理员可以确保在大规模 Linux 环境中实现高效的数据管理和高性能。

#3. Implementing Directory Indexing Techniques in Ext4 for Improved Performance 在 Ext4 中实施目录索引技术以提高性能

Optimizing Space Utilization for Large Directories in Ext4 File Systems

Optimizing Space Utilization for Large Directories in Ext4 File Systems

Optimizing Space Utilization for Large Directories in Ext4 File Systems 优化 Ext4 文件系统中大型目录的空间利用率

In the realm of file system architecture, particularly within Linux environments, the Ext4 file system stands out due to its robustness and scalability. 在文件系统架构领域，尤其是在 Linux 环境中，Ext4 文件系统因其稳健性和可扩展性而脱颖而出

One of the critical challenges in managing large file systems is optimizing the performance and space utilization of large directories. 管理大型文件系统的关键挑战之一是优化大型目录的性能和空间利用率

笔记：优化大型目录的性能怎么优化

As directories grow in size, containing thousands to millions of files, the ion of advanced directory indexing techniques.

随着目录的规模不断增长，包含成千上百万个文件，采用先进的目录索引技术变得越来越重要。

笔记：百万数量

Ext4 introduces several mechanisms to enhance the management of large directories, primarily through the use of HTree indexing, a variant of the traditional B-tree Ext4 引入了多种机制来增强大型目录的管理，主要是通过使用 HTree 索引（传统 B 树的一种变体）。

笔记：HTree indexing, a variant of the traditional B-tree

.HTree indexing significantly improves the performance of directory operations by allowing for a hierarchical organization of directory entries. This structure divides the directory into several levels, with each node in the tree representing a subset of the directory entries.

HTree 索引通过允许目录条目的分层组织，显著提高了目录作的性能。此结构将目录划分为多个级别，树中的每个节点都表示目录条目的子集

The root of the tree and each intermediate node contain indices to other nodes, which can be either leaf nodes containing actual directory entries or other intermediate nodes. 。树的根和每个中间节点都包含其他节点的索引，这些节点可以是包含实际目录条目的叶节点，也可以是其他中间节点

This hierarchical structuring allows for rapid location of files within the directory, reducing the time complexity from linear to logarithmic in terms of the number of directory entries.

。这种分层结构允许在目录中快速定位文件，从而将目录条目数量的时间复杂度从线性降低到对数。

Moreover, the implementation of HTree indexing in Ext4 is complemented by the use of dir_index, a feature that must be enabled to optimize large directory operations. When dir_index is enabled, Ext4 automatically constructs an HTree index for directories once they exceed a certain number of entries. This threshold is dynamically adjusted based on the average size of directory entries and the total size of the directory, ensuring that the overhead of maintaining the index is balanced against the performance benefits. 此外，在 Ext4 中实现 HTree 索引还辅以 dir_index，这是优化大型目录作必须启用的功能。启用 dir_index 后，Ext4 会在目录超过一定条目数时自动为目录构建 HTree 索引。此阈值根据目录条目的平均大小和目录的总大小动态调整，以确保维护索引的开销与性能优势相平衡。

Transitioning from the technical implementation to practical application, system administrators can enable directory indexing on an existing Ext4 file system using the tune2fs tool. By executing a command such as tune2fs -O dir_index /dev/sdX, where /dev/sdX is the device identifier, the file system is updated to support HTree indexing for all directories. This operation is non-destructive and can be performed without unmounting the file system, although a full file system check using e2fsck is recommended to ensure integrity and consistency. 从技术实现过渡到实际应用，系统管理员可以使用 tune2fs 工具在现有 Ext4 文件系统上启用目录索引。通过执行诸如“tune2fs -O dir_index /dev/sdX”之类的命令（其中“/dev/sdX”是设备标识符），文件系统将更新为支持所有目录的 HTree 索引。此作是非破坏性的，可以在不卸载文件系统的情况下执行，但建议使用“e2fsck”进行完整的文件系统检查以确保完整性和一致性。

笔记：简单 通过一个命令开启

In conclusion, the implementation of directory indexing techniques in Ext4, particularly through the use of HTree indexing and the dir_index feature, provides a robust solution for managing large directories. 总之，在 Ext4 中实现目录索引技术，特别是通过使用 HTree 索引和 dir_index 功能，为管理大型目录提供了强大的解决方案

Best Practices for Large Directory Structures in Ext4 File Systems

Ext4 文件系统中大型目录结构的最佳实践

Optimizing Space Utilization for Large Directories in Ext4 File Systems 优化 Ext4 文件系统中大型目录的空间利用率

In the realm of file systems, Ext4 stands out as a robust and widely adopted choice, particularly for Linux users. It offers significant improvements over its predecessors, especially in terms of scalability and performance with large directories. However, managing large directories effectively in Ext4 requires a nuanced understanding of its underlying structure and capabilities. This article delves into best practices for optimizing space utilization in large directory structures within Ext4 file systems, ensuring efficient performance and management. 在文件系统领域，Ext4 是一个强大且被广泛采用的选择，特别是对于 Linux 用户。与前代产品相比，它提供了显著的改进，尤其是在大型目录的可扩展性和性能方面。但是，在 Ext4 中有效地管理大型目录需要对其底层结构和功能有细致的了解。本文深入探讨了在 Ext4 文件系统中优化大型目录结构中的空间利用率的最佳实践，以确保高效的性能和管理。

Firstly, it is crucial to understand the concept of directory indexing in Ext4. Ext4 uses a feature called HTree indexing, which is a specialized form of hash tree. This indexing method significantly enhances the performance of file systems containing a large number of files by allowing for faster searches and retrieval. Without HTree indexing, the file system would have to sequentially search through directory entries, which becomes increasingly inefficient as the directory size grows. Therefore, ensuring that HTree indexing is enabled is the first step in optimizing large directory structures. This can typically be verified and managed through file system configuration tools and checking the file system state. 首先，理解 Ext4 中目录索引的概念至关重要。Ext4 使用一种称为 HTree 索引的功能，这是一种特殊的哈希树形式。这种索引方法允许更快的搜索和检索，从而显著提高包含大量文件的文件系统的性能。

如果没有 HTree 索引，文件系统将不得不按顺序搜索目录条目，随着目录大小的增加，这变得越来越低效。因此，确保启用 HTree 索引是优化大型目录结构的第一步。这通常可以通过文件系统配置工具和检查文件系统状态来验证和管理。

Moreover, the allocation of inode sizes in Ext4 also plays a pivotal role in managing large directories efficiently. Ext4 allows for the configuration of inode sizes at the time of file system creation. A larger inode size can accommodate more extended attributes, which can be beneficial for certain applications but might lead to wasted space if not utilized. Therefore, understanding the specific needs of your application and configuring the inode size accordingly is essential. For directories anticipated to handle a significant number of files or large metadata attributes, setting a larger inode size during the file system creation could prevent potential performance bottlenecks. 此外，在 Ext4 中分配 inode 大小对于有效管理大型目录也起着关键作用。Ext4 允许在创建文件系统时配置 inode 大小。较大的 inode 大小可以容纳更多的扩展属性，这对某些应用程序可能有益，但如果不利用，可能会导致空间浪费。

因此，了解应用程序的特定需求并相应地配置 inode 大小至关重要。对于预期要处理大量文件或大型元数据属性的目录，在文件系统创建期间设置较大的 inode 大小可以防止潜在的性能瓶颈。

Another aspect to consider is the use of directory entry caching. Ext4 supports directory entry caching, which helps in reducing disk I/O by keeping frequently accessed directory information in memory. This feature becomes particularly useful in scenarios where directories are accessed repeatedly, as it minimizes the need to read from the disk continually. Implementing caching mechanisms or optimizing existing ones can lead to substantial improvements in response times and overall system efficiency. 要考虑的另一个方面是使用目录条目缓存。Ext4 支持目录条目缓存，通过将经常访问的目录信息保存在内存中来帮助减少磁盘 I/O。此功能在重复访问目录的情况下特别有用，因为它最大限度地减少了从磁盘持续读取的需要。实施缓存机制或优化现有机制可以显著改善响应时间和整体系统效率。

Additionally, regular（定期的；有规律的） maintenance of the file system is indispensable for sustaining optimal （最佳的）performance. 此外，文件系统的定期维护对于保持最佳性能是必不可少的

This includes routine checks and rebalancing of the file system using tools such as e2fsck and tune2fs. These tools help in identifying and correcting any inconsistencies, potential corruptions, and optimizing the layout of the file system. 这包括使用 e2fsck 和 tune2fs 等工具对文件系统进行例行检查和重新平衡。

这些工具有助于识别和纠正任何不一致、潜在损坏以及优化文件系统的布局

Periodic checks ensure that the file system is in a healthy state and can continue to perform well under the stress of large directory operations. 定期检查可确保文件系统处于正常状态，并且可以在大型目录作的压力下继续正常运行。

方案：提供工具人工维护

Lastly, considering the use of additional tools or file system features such as quotas, access control lists (ACLs), and file system barriers can provide further enhancements in managing large directories.

Quotas can help in monitoring and controlling the disk space usage,

ACLs provide finer-grained permissions control

, and barriers ensure data integrity during unexpected power failures or system crashes. 最后，考虑使用其他工具或文件系统功能，例如配额、访问控制列表 （ACL） 和文件系统屏障，可以在管理大型目录方面提供进一步的增强功能。 配额可以帮助监控和控制磁盘空间使用情况，ACL 提供更精细的权限控制，屏障可确保意外电源故障或系统崩溃期间的数据完整性。

In conclusion, optimizing space utilization in large directories within Ext4 file systems involves a combination of enabling and configuring HTree indexing, appropriately sizing inodes, leveraging directory entry caching, conducting regular maintenance, and utilizing advanced file system features.

总之，优化 Ext4 文件系统中大型目录的空间利用率涉及启用和配置 HTree 索引、适当调整 inode 大小、利用目录条目缓存、执行定期维护和利用高级文件系统功能的组合。

By adhering to these best practices, administrators can ensure efficient management and robust performance of large directory structures in Ext4 file systems, thereby supporting the demands of modern applications and data-intensive environments.

通过遵循这些最佳实践，管理员可以确保 Ext4 文件系统中大型目录结构的高效管理和稳健性能，从而支持现代应用程序和数据密集型环境的需求。

Conclusion 结论

Optimizing space utilization in large directories within Ext4 file systems is crucial for enhancing system performance and storage efficiency. By implementing techniques such as directory indexing (using HTree indexes), increasing the inode size to accommodate larger directories, and employing directory entry compression, system administrators can significantly reduce lookup times and improve the overall management of files. Additionally, tuning the Ext4 filesystem with appropriate mount options and regularly defragmenting the file system can further optimize space usage. These strategies collectively ensure that large directories are managed more effectively, leading to better resource utilization and system stability. 优化 Ext4 文件系统中大型目录的空间利用率对于提高系统性能和存储效率至关重要。通过实施目录索引（使用 HTree 索引）、增加 inode 大小以容纳更大的目录以及采用目录条目压缩等技术，系统管理员可以显著减少查找时间并改进文件的整体管理。此外，使用适当的挂载选项调整 Ext4 文件系统并定期对文件系统进行碎片整理可以进一步优化空间使用。这些策略共同确保更有效地管理大型目录，从而提高资源利用率和系统稳定性。