第 7 章 丢弃未使用块 | 管理存储设备

But in fact, what I wonder is that if I use LVM to be an abstract layer between the actual SSD and the filesystem residing in it, can I still turn on the "discard" option, which is supported by the filesystem.

本文介绍了Ext4文件系统的挂载选项，包括日志模式、屏障写入、延迟分配等功能，以及如何设置挂载参数以获得更好的性能。

块丢弃操作允许 SSD 优化垃圾回收例程，它们可以通知精简置备存储重新调整未使用的物理块的用途。 要求 基本文件系统的块设备必须支持物理的丢弃（discard）操作。 如果 /sys/block/ <device> /queue/discard_max_bytes 文件中的值不为零，则支持物理丢弃操作。

Why do you think modifying the fstab would change the default mount options that stored in the filesystem metadata? Changing the fstab options will only change the options used at mount time.

In particular, file systems previously intended for use with the ext2 and ext3 file systems can be mounted using the ext4 file system driver, and indeed in many modern Linux distributions, the ext4 file system driver has been configured to handle mount re

discard 是 mount 命令的参数，在挂载文件系统时指定 discard 参数后，文件系统中删除文件后会自动触发 Trim/Discard 操作，通知块设备释放掉未使用的 Block 。