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398 lines
14 KiB
Markdown
398 lines
14 KiB
Markdown
---
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category: tool
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tool: zfs
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contributors:
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- ["sarlalian", "http://github.com/sarlalian"]
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translators:
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- ["Alan Cheng", "https://github.com/kedaio"]
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filename: LearnZfs-cn.txt
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lang: zh-cn
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---
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[ZFS](http://open-zfs.org/wiki/Main_Page)
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是重新思考与储存相关技术的结果，它把传统的文件系统和卷管理器集成到一个工具当中.
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ZFS不但有把它和传统存储系统分开来的特有术语，也有很多聚焦于可用性的功能。
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## ZFS概念
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### 虚拟设备（Virtual Devices，VDEV）
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对于操作系统来说，VDEV和传统的RAID阵列卡所呈现的raid设备类似。VDEV有几种不同的类型，每种类型
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都有自己的优势，包括冗余和速度。一般来说，VDEV的可靠性和安全性比阵列卡要好。因此使用ZFS时不
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建议使用阵列卡。让ZFS直接管理磁盘。
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VDEV的类型
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* stripe (条带。单个磁盘，没有冗余)
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* mirror (镜像。支持n-way镜像)
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* raidz
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* raidz1 (一个奇偶校验磁盘, 类似于RAID 5)
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* raidz2 (两个奇偶校验磁盘, 类似于RAID 6)
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* raidz3 (三个奇偶校验磁盘, 没有类似RAID等级)
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* disk （磁盘）
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* file (文件。不推荐在生产环境中使用，因为中间又多了一层不必要的文件系统)
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数据会以条带方式存储于存储池中的所有VDEV上。因此一个存储池中的VDEV越多，IOPS就越高。
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### storage pool （存储池）
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ZFS 使用存储池来作为底层存储提供者（VDEV）的抽象。这样可以把用户可见的文件系统和底层的物理磁盘
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布局分离开来。
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### ZFS 数据集（Dataset）
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ZFS 数据集类似于传统的文件系统（译者注：或者说是目录），但是提供了更多的功能。ZFS的很多优势也是
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在这一层体现出来的。数据集支持 [Copy on Write](https://en.wikipedia.org/wiki/Copy-on-write)
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快照, 配额, 压缩和重复消除（de-duplication）.
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### 限制
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一个目录最多可包含 2^48个文件, 每个文件最大可以是16 exabytes. 一个存储池最大可包含256 zettabytes 、
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(2^78) 的空间, 可以条带化地分布于2^64 设备上. 单一主机最多可以创建2^64个存储池。这些限制可以说是相
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当大。
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## 命令
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### 存储池
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Actions: （存储池操作）
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* List （列举）
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* Status （查看状态）
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* Destroy （删除）
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* Get/Set properties （获取/设置属性）
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List zpools （列举存储池（也叫zpool））
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```bash
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# 创建一个raidz类型的存储池(名称为bucket）
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$ zpool create bucket raidz1 gpt/zfs0 gpt/zfs1 gpt/zfs2
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# 列出所有存储池
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$ zpool list
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NAME SIZE ALLOC FREE EXPANDSZ FRAG CAP DEDUP HEALTH ALTROOT
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zroot 141G 106G 35.2G - 43% 75% 1.00x ONLINE -
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# 列出某一存储池的详细信息
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$ zpool list -v zroot
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NAME SIZE ALLOC FREE EXPANDSZ FRAG CAP DEDUP HEALTH ALTROOT
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zroot 141G 106G 35.2G - 43% 75% 1.00x ONLINE -
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gptid/c92a5ccf-a5bb-11e4-a77d-001b2172c655 141G 106G 35.2G - 43% 75%
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```
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Status of zpools （存储池状态）
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```bash
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# 获取全部zpool状态信息
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$ zpool status
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pool: zroot
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state: ONLINE
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scan: scrub repaired 0 in 2h51m with 0 errors on Thu Oct 1 07:08:31 2015
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config:
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NAME STATE READ WRITE CKSUM
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zroot ONLINE 0 0 0
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gptid/c92a5ccf-a5bb-11e4-a77d-001b2172c655 ONLINE 0 0 0
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errors: No known data errors
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# 用scrub来更正存储池错误信息
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$ zpool scrub zroot
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$ zpool status -v zroot
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pool: zroot
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state: ONLINE
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scan: scrub in progress since Thu Oct 15 16:59:14 2015
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39.1M scanned out of 106G at 1.45M/s, 20h47m to go
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0 repaired, 0.04% done
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config:
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NAME STATE READ WRITE CKSUM
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zroot ONLINE 0 0 0
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gptid/c92a5ccf-a5bb-11e4-a77d-001b2172c655 ONLINE 0 0 0
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errors: No known data errors
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```
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Properties of zpools （存储池属性）
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```bash
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# 获取某一存储池的全部属性。属性可能是系统提供，也可能是用户设置
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$ zpool get all zroot
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NAME PROPERTY VALUE SOURCE
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zroot size 141G -
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zroot capacity 75% -
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zroot altroot - default
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zroot health ONLINE -
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...
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# 设置存储池属性，下例这是设置comment(备注)属性
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$ zpool set comment="Storage of mah stuff" zroot
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$ zpool get comment
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NAME PROPERTY VALUE SOURCE
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tank comment - default
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zroot comment Storage of mah stuff local
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```
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Remove zpool （删除存储池）
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```bash
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$ zpool destroy test
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```
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### Datasets （数据集）
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Actions: （数据集相关操作）
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* Create （创建）
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* List （列举）
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* Rename （重命名）
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* Delete （删除）
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* Get/Set properties （获取/设置属性）
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Create datasets
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```bash
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# 创建数据集
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$ zfs create tank/root/data
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$ mount | grep data
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tank/root/data on /data (zfs, local, nfsv4acls)
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# 创建子数据集
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$ zfs create tank/root/data/stuff
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$ mount | grep data
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tank/root/data on /data (zfs, local, nfsv4acls)
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tank/root/data/stuff on /data/stuff (zfs, local, nfsv4acls)
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# 创建卷
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$ zfs create -V zroot/win_vm
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$ zfs list zroot/win_vm
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NAME USED AVAIL REFER MOUNTPOINT
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tank/win_vm 4.13G 17.9G 64K -
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```
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List datasets （列举数据集）
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```bash
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# 列出所有数据集
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$ zfs list
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NAME USED AVAIL REFER MOUNTPOINT
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zroot 106G 30.8G 144K none
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zroot/ROOT 18.5G 30.8G 144K none
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zroot/ROOT/10.1 8K 30.8G 9.63G /
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zroot/ROOT/default 18.5G 30.8G 11.2G /
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zroot/backup 5.23G 30.8G 144K none
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zroot/home 288K 30.8G 144K none
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...
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# 列举某一数据集的信息
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$ zfs list zroot/home
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NAME USED AVAIL REFER MOUNTPOINT
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zroot/home 288K 30.8G 144K none
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# 列出快照
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$ zfs list -t snapshot
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zroot@daily-2015-10-15 0 - 144K -
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zroot/ROOT@daily-2015-10-15 0 - 144K -
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zroot/ROOT/default@daily-2015-10-15 0 - 24.2G -
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zroot/tmp@daily-2015-10-15 124K - 708M -
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zroot/usr@daily-2015-10-15 0 - 144K -
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zroot/home@daily-2015-10-15 0 - 11.9G -
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zroot/var@daily-2015-10-15 704K - 1.42G -
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zroot/var/log@daily-2015-10-15 192K - 828K -
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zroot/var/tmp@daily-2015-10-15 0 - 152K -
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```
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Rename datasets （重命名数据集）
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```bash
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$ zfs rename tank/root/home tank/root/old_home
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$ zfs rename tank/root/new_home tank/root/home
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```
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Delete dataset （删除数据集）
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```bash
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# 数据集如果有快照则无法删除
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zfs destroy tank/root/home
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```
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Get / set properties of a dataset （获取/设置数据集属性）
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```bash
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# 获取数据集全部属性
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$ zfs get all zroot/usr/home │157 # Create Volume
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NAME PROPERTY VALUE SOURCE │158 $ zfs create -V zroot/win_vm
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zroot/home type filesystem - │159 $ zfs list zroot/win_vm
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zroot/home creation Mon Oct 20 14:44 2014 - │160 NAME USED AVAIL REFER MOUNTPOINT
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zroot/home used 11.9G - │161 tank/win_vm 4.13G 17.9G 64K -
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zroot/home available 94.1G - │162 ```
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zroot/home referenced 11.9G - │163
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zroot/home mounted yes -
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...
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# 获取数据集属性
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$ zfs get compression zroot/usr/home
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NAME PROPERTY VALUE SOURCE
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zroot/home compression off default
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# 设置数据集属性（下例为设置压缩属性compression）
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$ zfs set compression=gzip-9 mypool/lamb
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# 列举所有数据集的名称、配额和预留属性
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$ zfs list -o name,quota,reservation
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NAME QUOTA RESERV
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zroot none none
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zroot/ROOT none none
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zroot/ROOT/default none none
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zroot/tmp none none
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zroot/usr none none
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zroot/home none none
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zroot/var none none
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...
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```
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### Snapshots （快照）
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快照是ZFS 的一个非常重要的功能
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* 快照占用的空间等于它和原始数据的差异量
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* 创建时间以秒计
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* 恢复时间和写入速度相同
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* 易于自动化
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Actions: （快照相关操作）
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* Create （创建）
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* Delete （删除）
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* Rename （重命名）
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* Access snapshots （访问）
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* Send / Receive （发送/接收）
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* Clone （克隆。译者注：关于clone和快照的区别可参看[这里](http://docs.oracle.com/cd/E19253-01/819-5461/gbcxz/index.html)）
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Create snapshots （创建快照）
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```bash
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# 为单一数据集创建快照
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zfs snapshot tank/home/sarlalian@now
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# 为数据集及其子集创建快照
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$ zfs snapshot -r tank/home@now
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$ zfs list -t snapshot
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NAME USED AVAIL REFER MOUNTPOINT
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tank/home@now 0 - 26K -
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tank/home/sarlalian@now 0 - 259M -
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tank/home/alice@now 0 - 156M -
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tank/home/bob@now 0 - 156M -
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...
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Destroy snapshots （删除快照）
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```bash
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# 如何删除快照
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$ zfs destroy tank/home/sarlalian@now
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# 删除某一数据集及其子集的快照
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$ zfs destroy -r tank/home/sarlalian@now
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```
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Renaming Snapshots （重命名）
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```bash
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# 重命名快照
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$ zfs rename tank/home/sarlalian@now tank/home/sarlalian@today
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$ zfs rename tank/home/sarlalian@now today
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# zfs rename -r tank/home@now @yesterday
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```
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Accessing snapshots （访问快照）
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```bash
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# cd进入一个快照目录
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$ cd /home/.zfs/snapshot/
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```
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Sending and Receiving
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```bash
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# 备份快照到一个文件
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$ zfs send tank/home/sarlalian@now | gzip > backup_file.gz
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# 发送快照到另一个数据集
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$ zfs send tank/home/sarlalian@now | zfs recv backups/home/sarlalian
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# 发送快照到一个远程主机
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$ zfs send tank/home/sarlalian@now | ssh root@backup_server 'zfs recv tank/home/sarlalian'
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# 发送完整数据集及其快照到一个新主机
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$ zfs send -v -R tank/home@now | ssh root@backup_server 'zfs recv tank/home'
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```
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Cloneing Snapshots （克隆快照）
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```bash
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# 克隆一个快照
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$ zfs clone tank/home/sarlalian@now tank/home/sarlalian_new
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# 提升克隆，让它不再依赖原始快照
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$ zfs promote tank/home/sarlalian_new
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```
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### 汇总
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下面这个脚本使用了FreeBSD, jails和ZFS，来自动在一个mysql群集的热备主机上为一个mysq staging数据库
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创建一份纯净的拷贝。
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```bash
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#!/bin/sh
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echo "==== Stopping the staging database server ===="
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jail -r staging
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echo "==== Cleaning up existing staging server and snapshot ===="
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zfs destroy -r zroot/jails/staging
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zfs destroy zroot/jails/slave@staging
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echo "==== Quiescing the slave database ===="
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echo "FLUSH TABLES WITH READ LOCK;" | /usr/local/bin/mysql -u root -pmyrootpassword -h slave
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echo "==== Snapshotting the slave db filesystem as zroot/jails/slave@staging ===="
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zfs snapshot zroot/jails/slave@staging
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echo "==== Starting the slave database server ===="
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jail -c slave
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echo "==== Cloning the slave snapshot to the staging server ===="
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zfs clone zroot/jails/slave@staging zroot/jails/staging
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echo "==== Installing the staging mysql config ===="
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mv /jails/staging/usr/local/etc/my.cnf /jails/staging/usr/local/etc/my.cnf.slave
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cp /jails/staging/usr/local/etc/my.cnf.staging /jails/staging/usr/local/etc/my.cnf
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echo "==== Setting up the staging rc.conf file ===="
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mv /jails/staging/etc/rc.conf.local /jails/staging/etc/rc.conf.slave
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mv /jails/staging/etc/rc.conf.staging /jails/staging/etc/rc.conf.local
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echo "==== Starting the staging db server ===="
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jail -c staging
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echo "==== Makes the staging database not pull from the master ===="
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echo "STOP SLAVE;" | /usr/local/bin/mysql -u root -pmyrootpassword -h staging
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echo "RESET SLAVE;" | /usr/local/bin/mysql -u root -pmyrootpassword -h staging
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```
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### 延伸阅读
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* [BSDNow's Crash Course on ZFS](http://www.bsdnow.tv/tutorials/zfs)
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* [FreeBSD Handbook on ZFS](https://www.freebsd.org/doc/en_US.ISO8859-1/books/handbook/zfs.html)
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* [BSDNow's Crash Course on ZFS](http://www.bsdnow.tv/tutorials/zfs)
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* [Oracle's Tuning Guide](http://www.oracle.com/technetwork/articles/servers-storage-admin/sto-recommended-zfs-settings-1951715.html)
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* [OpenZFS Tuning Guide](http://open-zfs.org/wiki/Performance_tuning)
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* [FreeBSD ZFS Tuning Guide](https://wiki.freebsd.org/ZFSTuningGuide)
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